if you slip bobber was doing ok out of the water but not in, you likely have a slit or groove cut in the bead or top of the bobber that your line gets caught in when casted out from shore and the line is at an angle from the rod tip to the top of the bobber. Most cheap slip bobbers have this issue after a few outings with them. I replace all the plastic beads in the top of the bobbers I use with either glass or metal to prevent the 'groove' issue. Nothing worse than trying to fish 18ft down and your line won't go down thru the bobber after you cast it out.
Use unwaxed (round is preferred over flat) dental floss for your bobber stops instead of the pretied off the shelf stuff. When tied on properly and trimmed it will not catch in even the smallest guides or slip when casting or fighting a fish. It does need replaced on occasion especially if you make huge swings in the depths you fish. Like changing it from 20ft to 5 ft and back means you will have slid the knot 30 ft on your line. They will get loose when moving them alot. Just carefully snip it off with fingernail clippers and tie on another. One thing of floss in your tackle box will last years.
how are you tying this on your line??ive tried the little red rubber ones with holes in the endthe peach colored ones with holes all the way throughand the bright green thills that are pre tied and always manage to get them caught in my line guides its really agrevating having to adjust it all the time