Hi HippoSkinScoop and welcome to the forum
My JD-800, referred to in posts above, is now back together and happily working. You are right that it is relatively easy to get the red glue(p) out of the keys, but not easy to get it out of the contact strips, especially the little depressions in the rubber which you have shown in your photo. Furthermore the rubber strips do deteriorate and get a bit more brittle over time. They are held against the frame with a series of little rubber lugs that protrude through holes in the steel. My experience was that the old ones were difficult to push out (I used two fingers of one hand to push from the lug side and the other hand to simultaneously pull. It is very easy to damage them. And if you hit a problem (e.g. key contacts not fully cleaned) which you only find out when it is fully assembled, repeating the whole process is quite likely to be terminal. I ordered a set of contact strips from Syntaur in the U.S., who seem to have contact strips for the EP7, but you would need to check carefully.https://syntaur.com/roland_ep.html
I was really worried that these new set of strips might get damaged when being pushed in, but the new rubber is much more pliable than the old, and I had no problem in the end - using a cut and smooth-sanded wooden cocktail stick to push the lugs through.
I found this video (JD-880) incredibly helpful due to the systematic, patient way the guy explained everything.https://www.youtube.com/watch?v=5OWcU3UvF7c
Hope that helps, and good luck!