You're not giving us much to go on.

Can you provide some specifics about your recording and configuration?

How many parts?
What kind of parts?
Any arps?
Any motion sequences?
Any complex controller movements?
Any connections (USB or MIDI) to other instruments or your computer?
How long is the recording?

You mention 'waveform' but are you recording MIDI and then playing that back using Play/Rec?

Or are you actually creating a waveform file and then assigning that file as the source sample for an elelment?

The more info you can provide the better.

All I am doing is recording a piano "CFX Stage" to audio, then trying to play that back. I also have a nother recording from "Analog Pad" with no "complex controller movements" on a sepreate .wav that was recorded on the modx that will not play ether. One recording is about 1min 11sec the other is about 2min 57sec. The piano recording seems like it will freeze at 12 to 13 seconds, but not always sometimes it could be 20 or so seconds. The Analog Pad played all the way thru first time today, but then second time stoped at 12 sec. If I reboot the modx sometimes it will play back all the way thru. No Arps used. No conections to other devices. Not using for any source sample. No midi involved .wav file that was recorded from modx and being played backed by modx. I am playing this back from a usb stick that's been formated on the modx and has all my backups and only modx files on it, was never used for anything else. I guess I could try another usb drive and see if that is the problem. I just don't understand that it's not playing a .wav file that was recorded from the modx?

I will try a new usb flash drive and let you know.

I'd probably go with something like this:

https://www.bhphotovideo.com/c/used/429116/?smpm=bu_uar&gclid=Cj0KCQjwgNanBhDUARIsAAeIcAutkZWj1DyM1SohLyvVTHY374arsuPAQtjGFVqrNAK1o_IrhREIOokaApvbEALw_wcB

My selection criteria was:

1) On USB Compatibility List (under MODX+ downloads - applies to Montage and MODX)

2) Small size. I usually prefer 4gb since this ensures the filesystem will not be exotic for the larger sizes

3) Available to purchase from a trusted source (whatever that means to you - I won't express my biases here)

4) Trusted USB drive manufacturer. If it's on the compatibility list then it's already tested and therefore should be fine. I also have my own personal preferences for manufacturer that steer me towards some sticks over others.

I just don't understand that it's not playing a .wav file that was recorded from the modx?

I've assumed that those wave files always play just fine if played on a computer rather than the Modx.

If so that would seem to rule out any issue with the wav file itself. Though it might not rule out a USB compatibility issue.

This is the current list of USBs Yamaha provides
https://usa.yamaha.com/files/download/other_assets/0/1249530/DE_en_MODX678.pdf

The only other thing that comes to mind is if you have run into a memory issue.

I recorded some new wav files on the modx a few minutes ago and they play fine? The files that won't play I recorded a few months ago and I have updated the modx since then. I'm thinking maybe something in the old firmware messed them up? I tried to play the old wav files on my computer and they will freeze and lock up my computer? . The ones I just recorded play fine on my computer. I'm thinking it was the old firmware, but why?
Yes my san disk drive is on the compatibility list.

I think I'll just get a new flash drive and rerecord some of files.

I tried to play the old wav files on my computer and they will freeze and lock up my computer? .

Which raises the question: did the old files EVER play properly on the Modx (or computer)?

Is it possible that you recorded them but never played them back until just recently?

The ones I just recorded play fine on my computer. I'm thinking it was the old firmware, but why?

Which raises the question: which 'old firmware' were you using? What OS version were you using when you recorded the old files and what version are you using now?
https://usa.yamaha.com/products/contents/music_production/downloads/firmware_software/index.html?c=music_production&k=modx

There isn't much public info about the actual changes they make to firmware. The only source they provide is the Supplementary doc.

The latest version isV2.52 and the supplementary manual doesn't even mention that version.

And that link only lists V2.52 and V2.00 - it doesn't even list version 2.50.

The doc does have this for the 2.0 changes

The sequencer storage capacity (total User Memory) has been increased from about 130,000 to about 520,000 (for Songs) and about 520,000 (for Patterns).

Not sure what that means exactly.

They do have this change history page available
https://usa.yamaha.com/support/updates/modx_os_updater.html

V2.00 was when they added the pattern sequencer and I would expect it to have bugs that got fixed in the later versions but I don't know of any public info about what was done other than the Supp Doc.

I will take this opportunity to remind you, and others, of two things I recommend:

1. Perform regular backups of the system, and copies of other objects (waveforms, patterns, arps, files you create).

2. Test your backups and copies IMMEDIATELY after you make them to make sure they work properly.

Yes - I'm aware that step #2 seems like a burden. But a backup/copy is totally useless if it is corrupt or otherwise doesn't work.

Caveat Emptor!