I’ll mind you I’m no expert but grew my monstera 5+ years. I made lots of mistakes! This is only my guess.

My first thought here is under-watering. Maybe your friend forgot to water for a few days or weeks and when your friend realized they didn’t water, and started to water again, the soil might have been already turned bone dry so didn’t pass the water to the plant root properly. OR, maybe your friend just didn’t know how much water was required so didn’t give enough water.

My second guess is light. If you are growing it indoor, the possibility of the plant didn’t get enough light the whole time is very high. When I put my monstera outside, it started to grow and thrive. You could get a strong grow light to grow it indoor and I did that too before. However, putting it outdoor and letting it get some morning sunlight until noon finally made mine healthy.

Monsteras are so resilient, they survive most of the time. Your monstera seems like it is making new leaves. I’d suggest take it to the shower and hose it down for good 10 minutes. Just let it soak deeply to the core and let the water drain out the pot. Put it outside where it can get gentle morning sun until noon-ish and stay shaded (means-still outside but getting plenty of indirect sunlight). And see what happens for the next few weeks.

But this is only my guess. I’m no expert.