Some quick googling on this issue - and it appears a few people have this problem with the Mac - so it's not related to just the Yamaha keyboard. Have a look at this link and see if it's any help

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At the end of the day, it is an issue involving a Mac... Apple protocols are infamous for changing things. In a perfect world the current Mac OS remains in one place for long enough for all the third party applications and drivers have a chance to adjust. Since not all Mac users have your issue, it is probably caused by either your custom setup, or a conflict, or a power up issue or a combination of user error and any of the above.

Yamaha cannot do Apple support. At best, our folks may have some suggestion, simply by the chance they have run into someone with similar music related softwares as you and they may have heard of a solution. The companies making the software that is to run on the Computer can help you setup their specific product with the computer. When a conflict between it and something else occurs, you wouldn't expect one of the companies to answer questions about another company's product (they may just be unaware of that product). Both are probably individually working, it could be a conflict caused by two items negotiating for the Ports.

MIDI conflicts are usually simple, MIDI being so standard. (I would bet the solution here, when found, will be something very simple). But if you have a "DAW controller" (?) that might be negotiating for MIDI and Audio Ports... perhaps that is causing the conflict...the YSUSB driver is certainly negotiating for them. Sorry, I don't know what all you have configured... only you know. Perhaps you and 75 other people on the planet have your exact setup... who knows? You have an expectation that it should work correctly, and you're right, it shows. When I say an application Specialist - you need some one who can help you setup and understand the kind of software you are running.

But at the end of the day describing your issue to Apple support is your next step... it is an Apple support issue, if they deem it is problem with a specific device, then you will have helped the entire music community of users by providing the company involved by providing your information on your conflict.

If indeed it isn't an issue with certain Macs and the Yamaha's Steinberg driver we would want to know (that is something that is a major red flag, and would warrant immediate action). So please let us know what you learn.

Alright fellows I think I may have solved part of the issue.

Under the suggesting of Bad Mister I removed several MIDI components/drivers that was installed for the MIDI devices I have in MIDI studio.

I rebooted the iMac and turned on the Montage checked the MIDI Studio it picked up or initiated/loaded the Yamaha Steinberg USB drivers.

I repeated this several times and each time was a success.

There is still an issue when I turn off the Montage while My DAWs is open to test and see if I lose my Bluetooth and USB connections.
It still ejects external hard drives lose bluetooth connection to Keyboard and mouse and I have to hold the power button to the iMac to shut down.

I will try to contact Apple to see if they can do a diagnostic test hopefully they will not charge to much or nothing at all.

Thanks Again