As mentioned, a dry lube might help. This
is what I use to lube the slideout mechanism.
You might ask your dad to alleviate the presure from the seals. I have found these to stiffen up (especially in cold weather) where they seem to impede the slide from retracting back into the trailer. The seals can stick to the walls making it harder to retract and you can buy lube for these seals as well. I use slideout rubber seal treatment
for the rubber seals. Some people use baby powder, I hear.
Also, some slideouts can be adjusted, but he might want a tech doing this if he thinks its out of adjustment. I don't know what slideout you have so here's a link to the forum Library
where there are several manuals.