I know pictures would help, but I'm new so I can't link until I've posted twice. This is my second post, so I'll link pictures of the problem in a second.

Hi and welcome to TT. The first area I would look at is the segment, which is the most common source of sluggish/frozen keys. The segment is part of the type basket that resides under the ribbon cover. All the type bars pivot through it and it doesn't take much for that area to become contaminated and cause problems. Use a metal cleaner - I use Q-tip soaked in Varsol - to clean the pivot point for the letter Q. DO NOT use oil as it will only attract and hold more dust and dirt in the segment. At the same time check that its slug is resting at the same point as the rest of the slugs in the type basket to make sure that a linkage hasn't been bent.  

I have a Letter-Riter and Quiet-Riter, so if what I'm suggesting doesn't make sense I can take some photos later pointing to these areas. Good luck!