You're very probably running into the problem with Reality DB not being able to remove deployables or update their state after a server restart. I made a fix for this for use with 1.8 located here. I made it because I noticed tents weren't updating their inventories or being removed from the server if the server had restarted since they were placed. Though it's possible the same is true for traps since they are classed as deployables.
If that fix doesn't work, let me know and I'll try having a look at the coding in the file specific to traps and see if they also need a similar fix.
If that fix doesn't work, let me know and I'll try having a look at the coding in the file specific to traps and see if they also need a similar fix.