Amana XRSS287BB side-by-side freezer not cooling

Hello

I have an issue with my Amana side-by-side fridge, where the freezer part is not cooling properly / regularly and up to now intervention of a repair professional has not solved the issue.

The model reference is XRSS287BB, a side-by-side freezer + refrigerator.

The freezer part started showing temperature alerts (beep + red temperature light flashing) and obvious temperature drop in the freezer part. We unplugged the fridge and restarted it, which seemed to solve temporarily the issue, which occurred again after a few hours.

The electronic boards (main + panel) were then replaced but the problem appeared again.

Then the compressor was replaced.

The problem disappeared – but only for a while. It has happened again, although more rarely (restarting the fridge solves it now for a few days).

More precisely, I have measured the temperature inside the fridge and the freezer.

In “normal” operation (when there is no freezer temperature alert), I measure :
+3°C in fridge part (set at +5°C, so fridge is a little colder than what it should be)
-15°C in freezer part (set at -21°C, so freezer is a little warmer than what it should be)
Notably, setting the freezer at -21°C or -18°C does not change very much the temperature in normal operation, which remains around -15°C.

When the freezer temperature alert occurs, I measure :
+3°C in fridge part (set at +5°C, so no change in the fridge part)
-5°C in freezer part (set at -21°C, so freezer is much warmer than what it should be)

I have noticed that when left a few hours, without restarting, and with the temperature alert still flashing, the freezer temperature reaches again -15°C, so getting closer to “normal” state (although still warmer than the -21°C setting).

Also, when I restart the fridge, it goes to “normal” state (+3°C/-15°C in fridge/freezer for a setting of +5°C/-21°C).

Having changed the power board, the panel board, and the compressor, I’m a bit lost and so seems to be my repair guy – knowing that Amana fridges are not usual in France where I live.

I am thinking about 3 possible issues after visiting some American forums and looking at cases which had something in common with mine (although I could not find anything identical) :
– thermistor
– damper control
– defrost timer

Unfortunately, when I have asked my question on American forums I did not get any answer as this is a European Amana model …

Any idea or hint would be mostly welcome !