There is no easy way to spot this problem until it happens, and it can even happen with commercially produced tapes. Tapes can be damaged. A wrinkled or torn tape can jam a VCR as well as produce very bad video signal. If a VCR is dirty or has mechanical problems, it can mangle a tape and render it unusable. Sometimes it is possible to cut the tape in two and wind the good tape left into two different cassettes.
Some people suggest splicing videotape with clear desk-type cellophane tape.
This practice will almost certainly cause major problems with a VCR, and is not a good idea. Cheap tape will cause problems. If you are recording on, or have recorded on, very inexpensive tape you can expect to have more problems than if you use a better name brand tape. Off-brand and house brand tapes may use tape stock that is rejected by name brand manufacturers for poor quality. Video magazines and consumer publications can guide you in your choice of tapes.