It might be worth a try using a different power supply.
Actually, I do own a second Amiga and it does have its own PSU. It's also an original PSU, but a different model.
I tried it out, and poof - the problem is gone! It looks like the PSU is the cause. It took me a while to respond because I wanted to be sure first and made multiple power-off/power-on attempts with time intervals, and so far I didn't have the case where the computer wouldn't boot.
So, the two PSUs are:
- OK: Commodore A-300 Power Supply, 3.0A/5V / 500mA/12V / 500mA/-12V / T 2A
- NOT OK: Commodore A-500 Power Supply 4.5A/5V / 1A/12V / 100mA/-12V / T 1A
The NOT OK PSU is the original PSU for this computer (bought together from a friend 20 years ago). The OK one I bought later and separately.
What should I do now? Replace the PSU? Repair it? Who can repair? Is it even broken? Maybe I should just swap the PSUs between the Amigas (the other one is an A1200 with a Blizzard 68030 expansion)?
Do you have a friend who owns a CA-PSU?
I don't know any active amigans in my local area. Only folks who like to reminisce how they were breaking joysticks in half 30 years ago. I'd have to ask on the ppa forum if someone has this and lives nearby, but I think it won't be necessary anymore.
What speed is the ACA1234, and does the behaviour change if you increase/decrease the speed?
I'm running at 50MHz, but I tried different settings with acatool and to no avail. Even when I down it to 25MHz, the problem still happens.