We use a number of old APU1d4 and APU2e4.
For 6-7 years we had no problems at all.
In the last month 2 units APU1d4 stopped working. They are installed in two different companies, and a power surge in both units is unlikely.
Both cards have LEDs D10 and D11 always on, if powered with a working Power Voltage 12VDC/2A. No communication on the serial channel. Installed SSD cards are fully functional and could be installed onto backup boards.
If I use the two power voltages provided with the units (ANEN ENTERPRISE LTD), LEDs D10 and D11 blink very fast on both cards, and you can hear a noise like a relay switching on/off continuously.
It looks like the power supply is also damaged, even if it provides 12VDC (didn't check for ripples) and works with other unrelated systems.
I thought about the button battery, and I am afraid the same is going to happen to the dozens units we installed over time.
Any idea about a possible solution or test, to check if it is just bad luck?