I’m not even sure what’s going on in this problem, but I think that the solution is somehow connected with the self-inductance of the pulley
This question is taken from an olympiad booklet containing problems from Russian sources and some original problems as well, sadly the booklet doesn’t have solutions. Link to that book: Pathfinder for Olympiad and JEE Advanced Physics-Arvind Tiwari, Sachin Singh - - PDF Drive , This question is from Chapter 13 Electric Current, Challenge Your Understanding, Question 2. A small hint is given at the back of the chapter in answer keys.
You can share your own ideas on this problem as well.
Solution I found on YouTube today(in english): PATHFINDER | CURRENT ELECTRICITY | CHALLENGE 2| CHLYU 2 - YouTube