In general, I found the reason why the voltage was dropping.
Resistor number 2 in my photo or R4 according to the datasheet should be 20 Ohm, I measured it and it seemed to be 22 Ohm, but when I decided to recheck all the components of the strapping by unsoldering them and measuring the ratings, it turned out that this resistor is not quite stable and one of its terminals has some kind of defect, very poor contact. I replaced it with 24 Ohm and everything worked, it holds a load of 7.5 Ohm easily.
I have one last question, how critical is it to leave 24 Ohm instead of 20 Ohm? The other 3 microcircuits have 22 Ohm resistors.
Thank you again for your support.