Does the PINDA sensor change over time?  

Does the PINDA sensor change over time?

I have a MK3 that's almost 4 years old and has worked well up until about a month ago. 

Over the last month or so, sometimes when laying down the first layer, after a few minutes the extruder starts to "click" and obviously has trouble feeding filament. I pause the print, check the first layer, and find that it appears to be trying to extrude too close to the print bed. So I adjust the Live Z up about 0.05 to 0.10 or so, and all is well for more prints. Days later, same situation occurs and I have to once again adjust the Live Z up more. These adjustments are cumulative - the previous adjustment was still in effect. Over the last month, this keeps happening. 

I've checked and the PINDA sensor is tight, the nozzle is tight and clean, and the printbed is fine. I'm using Prusament. 

Once the first layer is down, the rest of the print is normal. On a large print it will happily continue for hours without a hiccup. 

Any insight into what might cause this? 

Thanks.