Anyway, we had problems with the 7805 regulators shutting down from
overtemp. They were mounted on the PCB with a small heatsink.

Hi all,
overheating should not be neglected. In my professional life I
encountered a device made by a famous company, which had a 7805 on a
heatsink, a processor and several customer chips inside a tightly
closed plastic box. All was O.K. at power-up. I was called for service
after two days. The device was hot and really did not work. I let it
cool down and all was O.K. again - for next two days. I was forced to
remove the top cover of the box forever. The device has been working
for several years now.
Proper cooling seems to be a must.

BR from Ivan OK1SIP