Random command failure

Commands fail randomly. Occasionally, a perfectly fine command such as /tp @s ~₁₀₀ will return a syntax error. Sometimes, other commands, such as /tag, /scoreboard, or /setspawn will not return anything  in the console or in the chat. When that happens, sometimes they work, sometimes they don't. I've attempted a fresh install on a newly generated world over 15 instances today. I can't find a pattern or trigger.