Ps4 Slim too loud despite cleaning?

In the past, I have been able to fix my friends and me's controllers a number of times. I was even able to clean and repair my friends' consoles with no problems. Personally, I also clean my Ps4 (slim) regularly and once a year completely from the inside (have had the console for a little more than 2 years). A week ago I noticed that the fan on the Ps4 was getting unusually loud while playing, even though the console didn't get too warm. I then decided to open the console and clean it (as I said, the last time I opened it 6 months ago). After I cleaned it and closed it again, I noticed that the fan still had an annoyingly high speed when starting a game. I opened it again to check whether everything was really okay, but I didn't find any faulty components (the fans look good, thermal paste is okay, no broken cables, no component looks damaged). What could be the reason that it suddenly became so loud? As mentioned, the problem was BEFORE I opened the console.

That you have opened it so far and that the WLP is no longer completely correct, you should also replace it, actually it should always happen when the console is opened that far.

WLP switch to a good one.

What is a WLP?

WLP stands for thermal paste.

Thermal paste is a thick liquid that is applied directly to the processor, or in this case the APU (i.e. Processor with integrated graphics unit). It ensures that the waste heat generated in the APU is passed on

Oh yes, I knew what the thermal paste was, just didn't know that it would be abbreviated