Bob,
I just had this issue, look on the top of the opener - check the sprocket that pulls the chain, is it bent/cocked? If so, there’s a gear assembly inside that probably isn’t driving the up/down limit sensor…the nice part is that Sears made these VERY repairable, and you can order a new gear/sprocket part for about $14 - and it will be whisper quiet.
Here’s a link to an Amazon part that fixed my 2000 door opener, ***check your manual for the specific part.***
https://www.amazon.com/dp/B097YPWC6J?psc=1&ref=ppx_yo2_dt_b_product_details
Reach out to me if you have specific questions.