My Macbook air keyboard has been glitching but it usually went back to normal but this time it didn't

Solution 1:

Taking all the symptoms together would suggest a water spill.

The initial spill caused short-circuiting of the Shift key [switch permanently closed] which eventually dried & 'recovered', but later corrosion has now affected the circuit tracks across the keyboard. Diagonal lines of affected keys, 5, T, G and -, [ are indicative of circuit board damage [switch permanently open].
After comments re the initial 'spill' being very slight, the later damage may not be related. It could have been done by impact, bending or twisting.

Long-term, this will need professional service or even replacement.
Short-term I'd look at getting a cheap USB keyboard.