What is the version of FCPX and what is the codec of the clip it gets stuck on?
Transcoding takes a lot of additional space. If any of that space is on the problem drive, that could cause FCPX to hang or malfunction. Even if the library and FCPX cache are on the system drive, if media is on a problematic external drive that cause cause FCPX to hang.
By “errors” if you mean the system volume, that can only be checked & corrected by Disk Utility First Aid if the system is in recovery mode. Otherwise it is a read only test. To boot into recovery mode hold down CMD+R when powering on. Then select Disk Utility and run First Aid on the system drive. Although that should be safe, it’s best to have a backup, esp. if you suspect disk reliability problems.
Disk Utility only detects and tries to fix file system problems. It does not do a surface scan and cannot fix bad blocks.
You could try DiskWarrior but that does not work on APFS only HFS+.