Hi Ron,
There are at least following entities that may affect to the received signal strength in wsjt-x:
Your FT5000mp
Microkeyer
Sound card, especially when it contain analog gain setting
Windows Recording settings including Mixer.
If I understood correctly a change of the sound card does not affect and can be ruled out.
Also Windows settings seems to be ruled out.
What about the Microkeyer? Have done any settings on it e.g. die to use it for other modes?
I would not rule out your rig as well. Any possible change there?
73, Reino OH3mA