Wandering trader llamas won't despawn if the lead that keeps them with the trader breaks. This issues affects all versions of minecraft bedrock.

Sometimes wandering traders spawn underground, in the caves underneath my base or underneath a village.
When they spawn underground, their leads might break cause llamas got stuck and can't reach the trader. Once their lead breaks, llamas won't ever despawn.

I checked the caves underneath my 1 year old base and I found about 12 llamas in a ~3chunks range. They were just sitting there forever, causing lag and performance slow down.

My suggested solution:
I suspect that they won't despawn cause they're wearing those blue carpets, so make any untamed llama that's wearing a blue carpet despawn