And I have had to replace bearings in Crayford focusers twice. They can wear out.
Symptom is play and excessive tension on the pinion adjustment screws is required to keep the focuser tube from deflecting away from the rear bearings under load and my bet is that if the front pair of bearings are wearing, it is only a matter of time before the OP starts to experience more serious symptoms and potential damage to the focuser.
The front bearing pair is the pair that will wear first because it carries much more of the load. The pinion acts as a pivot point and the load acts like the bigger kid on one side of the seesaw so that the front of the weight is being focused on the front of the focuser tube. For scopes that have a fixed orientation (Newtonians and refractors with Alt-az mounts or rotating focusers) the front bearings do all the work really. The rear bearings just kind of guide the tube and keep it from shifting side to side.
And the bearings in these scopes are tiny. I don't think they are really up the task of heavy laods.
I notice that Moonlight now sells heavy service Crayfords with two pair of dual bearings at each point.
In other words, while the OP only has four bearings, the heavy duty 2.5" Crayfords from Moonlight now have sixteen bearings!
(The damage that occurs with front bearing failure is that the bearing will start to drag on the tube. This drag will cause marring in the tube surface and this will cause slight roughness in the motion of the focuser.
The bad news is that once this occurs, if it is serious enough, it does not go away when you put in the new bearings and you have to carefully smooth the roughness with suitable tools.
You can't take off two much material. Ask yourself what happens if you cut one leg of a chair slightly shorter than the other leg and you will know why I am saying this.
So, that is why I would be looking for the problem sooner rather than later. If you scuff or mar the tube finish it can cause a very slight degradation of the silky smooth Crayford focuser movement.
At the first sign of a bearing dragging, stop using the focuser or the damage will quickly build.