Why does GBoard have inconsistent "space to use autocorrect"?

My GBoard is having so many issues with how it autocorrects next work suggestions. Generally if I hit space bar it automatically inserts the suggested word from the suggested word row above the keyboard. But then for seemingly no reason it does not do it for some words. For instance: brain. If I type "brakn" ... And hit space... Hit inserts "brain", which is what I want! But if I type "braim"... And hit space... It does NOT insert "brain" even though it is the suggested word... It just keeps braim and underlines it to show it is spelled incorrectly. It's driving me insane. I have cleared my cache and installed / uninstalled. Why doesn't space bar ALWAYS insert the recommended word, it only happens some of the time.