YG-455C-1 seems defective.

Any link to that previously documented issue?

 

What is the settings for the slope tune? Both should be wide open.

 

Wide open, either with Narrow Engaged or not. But does affect receive bandwidth when cranked and the one filter is in line

 

Should be familiar to you.

https://forums.qrz.com/index.php?threads/couple-of-ts-930-question.651172/#post-5007006

 

930, not the 940.

 

For all intents and purposes, no difference whatsoever. These are carrier-board (rather than solder-in) filters - and the board joints have proven troublesome, as my comment in the linked post pointed out.

ETA:

Also have a look at this post and the parent thread: https://forums.qrz.com/index.php?th...1-ts-940s-question.477299/page-2#post-5533410

 

A nanoVNA can test filters like these in s21 ( transmission ) mode. I have used it to repair several Kokusai mechanical filters at 455 kHz with bandwidths of 600 Hz and 2.4 kHz. Price about $35 delivered.

 

obtained another YG-455C-1 filter, installed, and radio works so appears it was a defective filter. A first for me.