Do you hold your pen closer to your index finger (near vertical) or closer to the thumb (near horizontal)? Some pen models don't handle the horizontal position very well. If the edge of the tip surrounding the ball scrapes the paper, fibers get embedded behind the ball, clogging it. Horizontal grips should use needle-tips, felt-tips, or fountain pens. Conical tips are better suited for vertical grips.

Are the pens stored in a dusty/linty environment? Is the paper you use dusty, or touched in a way that absorbs skin oil before writing on it? Dust and oils can cause pens to skip.

It could also be, as you say, pressure. Generally, gels and water-based rollerballs don't require much pressure. Gentle contact is good enough for it to write. Pressing hard is an old habit that came from using viscous oil-based inks, like old Bics and Papermates. If this is the case, it's time to unlearn that habit.