2nd day printing with the Prusa i3. Parts would not stick, and I was scratching my head for awhile on the issue.
Decided to go back and check the screws on the base of the print bed, and there were some that were loose. The print surface also looked a little bowed in the middle.
After tightening the screws and recalibrating again, everything sticks perfectly again. Whew!
Likely was caused by the heating and cooling of the print bed. Should I add some threadlock to the screws there?
Make sure there is some tension on the springs. This will HELP but not completely eliminate the bed changing position. With all the movement and hot and cold cycles on the bed, things WILL get out of adjustment.
The only way to avoid constant adjustments is to outfit it with some kind of autoleveling.
In the meantime, you can mod the bed so that you lock bolt in place at the top (on the bed), drill out the threads on the mount, and print adjusting knobs for the bottom. Lots of variations for this on the Internet and Thingiverse.