Hi Amber,
First thing I would check is string tension. Dead or uneven strings can really reduce stability on off-center hits. ^^

I’d start by checking the strings too. If they’re old or unevenly tensioned, off-center hits can suddenly feel much harsher.

Has anything changed recently with your setup?
New string, different tension, overgrip, vibration dampener or even a bit of lead can change how stable the frame feels.

If the racquet only feels unstable outside the sweet spot, I’d also check whether the stringbed has simply gone dead.
Sometimes the racquet itself is fine, but the response becomes much less forgiving after several hours of play.
A fresh restring at your usual tension would be an easy first test.