The Grease zerks for the linear bearings in the Panel Pro 5925 and 6126 utilize a m6 x .75 or 1 thread depending on the bearing manufacturer. Using a standard grease gun, sometimes the chuck (the part of the grease gun that comes in contact with the zerk) either does not connect well so you have this great gob of grease on the outside that does nothing except make a mess. Or does not release and you tear out the grease zerk from the bearing as it is threaded into a very thin sheet at the end of the bearing. At this point bad words are spoken, grease guns are thrown, etc.
Since the existing zerk threads are stripped out, what do you do? Go to your favorite farm store and get some 1/4 x 28 grease zerks. they will thread into the stripped out 6mm hole.
Next thing is get a good grease fitting. Lock N Lube has one that attaches without leaks and disengages easily.
The next challenge is getting into small spaces like the bottom of the z axis. Use the Lock N Lube needle dispenser.
the tip of the needle pokes into the grease zerk where the grease goes in.
This will eliminate most of the bad words that are spoken when it is time to grease. Grease the 12 zerks once a month and dry the rails with a rag wet with WD40 after use.