Suddenly unable to type in signs, potentially after alt-tabbing out of the game

Regularly, when i type in a sign, the game will stop recognising my typing. The only way to fix this is to restart the game. I think it might be due to me tabbing out of the game to check something, but when i tried to reproduce it, it didn't occur. Could this also be due to me running it on a minecraft realm or my only resource pack, Classic Faithful x32 Jappa for bedrock?