Mac mini M4Pro, External NVME Hangs when two enclosures connected

I have a MM M4Pro, and have 2 external NVME SSD Enclosures connected directly via two separate Thunderbolt 5 ports/cables.

the same problem happens on 2 x Hyper USB4 SSDs or 1 x Hyper and 1x Acasis TB3 enclosures and WD SN850X Ssd's.

If I attach the devices with the Mac running, all is good, good access speeds and useable drives as I would expect

If I turn the Mac off and reboot, one of the enclosures will hang and disconnect the drive once I try to access it, the other works fine.

System Info shows the USB4 devices on the right bus, but the Acasis appears to be on the USB3.1 Bus, when cold booted.

I don't intend to leave the Mac on so not being able to cold boot when connected is an issue. anyone have any thoughts on the cause?

Given this seems to work fine once running is this likely to be a power issue on the Mac? does the start up power on an SSD cause an issue with the MM Thunderbolt 5 bus? or is my MM M4 Pro faulty?