Shadow JM35 Issues

I have my 3rd Shadow flashlight and second JM35. The first quit on my after a few uses and Banggood wouldn’t warranty it. I bough another and it’s giving me issues.
I added an extension to the recent JM35 from the prior light. It turned on but would not shut off. I tried different cells (mine were quite long). I tested the light a couple times and it worked well.
Yesterday i turned the light on and after turning it off, half the LED remains dimly lit. I have the XHP-35LED.
This is strange behavior from a light. Anybody have input?
I contacted banggood and no answer to date.

Can you provide a link to the flashlight you have?

You said XHP35. Did you mean XHP50?

Does your light have a tail switch or just a side button?

I have seen on the banggood site that there are two versions, one with the extension and the other without. clearly they are not interchangeable….???

neither light had a tail switch

sorry, XHP50 led

Think product page mentions about 1- and 2-cell incompatibility.
Anyway see this post:

Note: Not sure if older versions allowed mixing 1- and 2-cell versions.

My understanding of the Shadow JM35 is that the ones with the clicky on the rear are only compatible with 2x 26650 and the ones that don’t have the tail clicky are only compatible with 1x 26650 and they are not interchangeable. No 1X 26650 in ones with tail clicky and no 2x 26650 in ones without tail clicky. I have a few of these lights and the same is true for me.