Careful with degreasers, some degreasers will be perfectly suitable, others not so much. Soapy water and a soft brush usually a good start with calipers.
First, do the levers return when they stick? And apart from the sticking is the lever feel consistent? It’s possible it’s a brake fluid issue but it wouldn’t be my first assumption. And Oro m/c seals are very durable
If it was mine there’s various things I’d do tbh, I’d be checking the levers are moving freely and also checking the calipers are pushing reasonably equally first.
Oros have 2-piece calipers so providing you’re comfortable with the work, the best bet if it’s sticking at the caliper end is to strip them right down, get the pistons out, check and clean the seals etc. (easier to do this with split calipers than with monoblocks but there’s tricks to it). Replacement seals and pistons are available but it’s a reasonable expense so unless things look worn I’d try again with the original ones. Trying to clean them with the pistons in might work but if they’re gummed up enough to stick on then I’d be a bit surprised if it does tbh.
