Some of the probe housing do actually crack due to the quality of palstic material used in them. This is commonly seen in GE probes linear and convex esp 546L C348 etc The cracks appear as hairline ones at the corners and with time the cleaning slutions and gels seep in through them causing delamiantion of the lens material (rubber housing)and eventually casuing element failure.
GE has addressed this issue to a certain extend in their new probes.
These cracks can be repaired and the whole housing repainted and tested for electrical safety. I am sure there a lot of companies in US which provide these services.
