Electroincs related question.

I have a Foxeer TM600 vtx which developed very bad reception and range for some unknown reason. So I read online that removing the RF shield might help because the shield might be too low and touching the electronics underneath. 

I gave that a shot, and it actually worked! 

Then without making any modifications to the shielding, I soldered it back on with only a few dots of solder around the shield. Then I tested it again...the bad signal and range came back!! 

Now, the guy in rcgroups said he stuck some electrical tape inside the shielding. When I checked my shield, it already had something that looked like masking tape already stuck on. 

Does anyone have any insight into this?

They had a first batch that had the problem like you describe, but that tape inside was added to resolve it, maybe contact the seller and arrange replacement?

I had the same problem and it turns out I was on the wrong channel. There are a few channels that are very close and you can still get clear signal nearby but your range will be reduced.

I already tested all channels. And don't forget its fine once the shield is off.
FYI, i resoldered the shield back on giving a tiny bit more space underneath. The picture is clear and clean again!!