Most common defective components

Actually all of the above options can be voted for. Logic board repairs are quite unique and every single repair is different as it comes with a different source of issue (eg. liquid damage, mechanical damage, power/LAN/USB surge, component failure, battery issue etc). Many of modern machines based on a hybrid CPU (CPU+GPU+PCH in one chip) quite often suffer from hybrid CPU fault (but this strongly depends on manufacturer).

To get an accurate answer for your question, you should search for all resolved topics on our forum and find out what is the most commonly replaced component - for better statistics, you shouldn't limit that research to 10-20 topics but view at least 200-300 recently resolved topics.

mladen82 wrote:I wanted to hear what the experiences of other colleagues

As I said, you can find an experience of other colleagues in RESOLVED topics, which are the best source of information. Please do not expect any advanced statistics until you do them by yourself (why, please find my answer below the following quote). Again, as I said, many different reasons of damages cause even more possible failures. Now multiply it by the number of logic boards manufactured across the whole world (although most of them are built in similar way, they all have some specific weak points).

mladen82 wrote:It may be better to ask the question, which defects are the most common, but in percentages.

I'm afraid nobody keeps such statistics for one common reason - people in workshops do not have enough time to do so. The other problem is that some people ARE able to do a certain works while others AREN'T. Let's say, you have 100 identical laptops to repair, none of them turn on. If you are less experienced in laptop repairs, you won't be able to cross a certain point in diagnosis (your diagnostics ability ends at some point, it may be caused by lack of service equipment or just lack of knowledge). After replacing BIOS and KBC you come to the conclusion that there is a high chance that all those laptops need a hybrid CPU replacement (you suspect a PCH part of APU). Then I get all these machines into my workshop and quickly discover that only 10% of them need hybrid CPU replacement, 25% need power circuit repair (SMPS driver and/or MOSFETs), 37% need KBC programming (you did not know that new KBC on this model needs programming!), 6% have a mechanical damage and they can only be written off (it is my conclusion only but there may be the chance that someone else is able to fix such mechanical damages), and the remaining 22% need just small components to be replaced (like resistor, capacitor etc). Two workshops, two completely different statistics. Too many factors causing such statistics quite unreliable. That's why you should read RESOLVED topics, which only point to the REAL faults found on logic boards in case you require much more reliable statistics. Quite huge job but the only option that makes sense.

Another example - I only fix Apple machines. In my workshop I have a lot of screen/keyboard/battery repairs, a lot of component level repairs (mostly liquid spillages), some percentage of EFI works (corruption, ransomware, forgotten password) and low percentage of BGA repairs (just a small number of models). For those who repair Dell, Toshiba and Lenovo laptops the statistics will be completely different.