Sign Text Being Wiped on Minecraft Build

Question:
Me and 2 other people are making a CTF map, and we're so close to finishing! The only thing left to do is to restrict the map, and we're using signs, since they make it easier to restrict things with greater precision, even if they take more time to place. However, we're having a problem with the signs. We're getting this error message an error message about being unable to locate a sign at a specific set of coordinates, and those coordinates lead to a sign that for some reason has lost its text. While we could normally just replace the signs with ones with text, for some reason, more and more signs keep losing text, even if we had replaced them earlier. While we could certainly just use silverfish blocks, we'd rather not go through that if we can fix the issue with the signs.
Is there any way to fix this issue? We've tried copying a correct sign and doing "//replace sign #clipboard", and we've tried manually replacing any wiped signs. I just wanna know if it's fruitless to search for a fix to this if I could spend less time just using silverfish blocks.

Thanks so much!

Edit:
Links to pictures of the wiped signs, and the error message (respectively):
https://cdn.discordapp.com/attachments/506531041184579596/508467888781393930/unknown.png
https://cdn.discordapp.com/attachments/506531041184579596/508464407316004874/2018-11-03_22.15.07.png