Z axis endstop fix on Davinci 1.0A

I run a Davinci 1.0A with Repeitier V1.0.6. Ran fine for months. Then the other night I started a print and it was trying to HOME and I heard a terrible grinding noise. Turns out the bed was moving upward and kept going ramming itself into the mechanical stop. No errors displayed just terrible grinding. After about 3 hours of troubleshooting I determined the problem was the Z stop sensor was not being activated. It appears to be light activated with a metal strip breaking the beam. The metal strip appeared to be doing so at the top of the travel but was not being sensed by the CPU. I then lowered the bed and began a manual Z Home. As the bed rose again, I stuck a flat object into the sensor and presto - The bed stopped. So this proved the sensor was functioning okay, so it had to be an alignment problem. But nothing seemed to have shifted. My fix was to place a small strip of black electrical tape on the leading edges of the metal strip to extend its surfaces. This appeared to do the trick and after a bed alignment I completed 2 prints already with no problem. However, I can't believe the tape is a permanent solution. I suppose I have to improve on this. Has anyone seen this before? And have your own fix?