Trailer bunks and roller not staying in place?

I have a 2013 EZ Loader trailer and I put guides on and I made a few minor adjustments after I got the boat and trailer last year. The boat always went right on the trailer power loading or loading by hand on the electric reservoirs even loading by myself. Last couple times out the boat has been a total nightmare to get on the trailer straight. I got to looking at it today after I got home and noticed the bow roller was pushed forward almost a foot and the front of both bunks was shifted over 4-5". I moved everything back and if it happens again I'm going to drill holes and put a bolt through the brackets instead of just clamped over the frame and rails. Anyone else have issues with their trailer bunks or rollers?

I have not had this problem but I would have to consider not drilling though a frame member.
Any time you drill a hole in a tube, round or square, you compromise the rigidity of the structure.
Unless you plan to re-fit the trailer for another boat in the future, I would consider tack welding the bracketry in place.
You could make the welds very small so in the future if you had to you could remove them with a die grinder or cut off wheel.

The trailer is galvanized so I'd rather not try to weld on it. One 1/2" hole for each bracket is not going to hurt the strength of the trailer at all. The only reason the brackets are clamped instead of bolted from the factory is to allow for them to be easily moved around for different boats.

Bolt away!

I have same EZ loader trailer and my 17ft tin boat didn't match trailer bunks from the start with out re- adjusting bunks to line up with the hull. It came without side bunks, but I added some on to help the guide on and I have a 2 x4 that I use to help me push the boat over if I need to.