So I was making linked portals using command blocks for my realm so I realized that after I had typed my command in I left the command block to do other command blocks so when I came back to the command block the command was replaced with #' which made the command useless infact all the command blocks where replaced with #' because all the commands blocks where sharing similar commands. I don't know if it does do it with outher commands but the command I was using is an /execute commad

I checked for spelling errors the second time I pasted the command in there where no spelling errors but there where still #'.