Web Crawler stucks in Pending status

Hey guys. I'm trying to execute several crawl jobs one after another. Each job starts in a different engine.
The first job is working perfectly. After SUCCESS I delete the engine and create the new one where I try to start a new crawl job but the status of this job is always PENDING. The only way to get rid of this is to redeploy App Search. This behavior is reproduced in docker-compose deployment and in stand-alone deployment on EC2 instance.
Do you have any suggestions what is the reason for this issue?

When you start the second crawl, what does it say in the logs? There should be clear set of messages about the progress of a crawl request: it should be created when you click "start crawl", then it should be picked up by the CQM (crawl queue manager component of the product) and a new crawler worker should be started... If it always stays pending, that could mean that the solution has no more capacity (crawler worker threads) left and you need to wait for active crawls to finish or that the CQM is dead (which would be bad, but should never happen).