If I recall there are two shoulder bolts that pilot/locate the side cover. One in each end if I recall. No reason to loosen bolts and tap the cover if these bolts are properly located.
If the shifter moves freely there is no issue. What you likely are feeling using the operating lever is the decent mechanicism rolling over the detent ball. Much like an auto trans lever rolling over the detent ball. As you go over the tip the effort rises then falls.
When adjusting the shifter you are supposed to place a drill rod or hex into the bottom of the shifter to align all the shifter levers in the neutral position before adjusting the rod ends to engage the shift levers in he cover.
Good advise, but there are occasions where you need to "swim" the side cover around to achieve smooth operation and proper detent, alleviate binding, stiffness, etc, etc, esp when the OP has had it rebuilt/serviced and it really hasn't seen any usage, a lot of factors here we can only surmise at...
We'll assume the OP is well versed in shifter set up/assy and operation?
