An issue which was falsely claimed to be a duplicate

Might relate to MC-87872, but I cannot confirm this
Does this still happen to you or only once?

Yes Marcono, it still happens to me. I just got done trying other commands to target myself after dying and respawning such as "kill @p" and "execute @p ~ ~ ~ summon Creeper", and both claimed that "the entity UUID provided is in an invalid format." I also tried replacing @p with @a, and nothing happened to me.

Have you reopened the world before further testing?
If not please force a crash and attach the crash report

Might be MC-89361.