What Abby said is correct and the most natural for the context. It would be used by natives. Unpleasant better fits the scene and the incident. Undesirable is ok but is used to describe effects or consequences etc. Undesirable. adjective not wanted or desirable because harmful, objectionable, or unpleasant. not wanted, approved of, or popular: it has a very small interchange with unpleasant in a dictionary but undesirable is more used like this parents to child "I wish you would move away from that undesirable neighbourhood"

Hello Pelin, They are all good sentences, but I would replace ‘undesirable’ with ‘unpleasant’. It sounds much more natural and native. “Some unpleasant scenes happened here.”

Here are suggestions Some undesirable incidents happened here Give me a call once in a while

I would say Some undesirable things happened here. The others are perfect!