Have you tried pushing the piston back a little, grease the slide pins (red rubber grease) then refit everything then go for a drive?
Sticky pistons can be eased and can be ok, sometimes they will need replacing/a refurb also.
Just a suggestion, I’d try first.
These cars calipers don’t need any encouragement to seize, keep them operating, serviced/lubed or they cause trouble. Best replaced if it gets to that with an OEM caliper or refurbished of the same.