200D CHANGES POWER OUTPUT x 2-CALIBRATION INTERMITTANT

[KA1GXR]

Greetings:

Have had this issue off and on since last year. Same issue all bands. Testing with dummy load when calibration maximum power out to 100w on all bands. Months ago I replaced the original fuse holder with a beefier one using a larger blade fuse type. I have kept screen shots of my PA Cal. screen to be sure numbers are not changing. Latest Thetis 64 bit firmware 1.8 Orion.
I calibrate 80 M for example setting 56 for 100 watts measured slider at 100. All seems well for weeks of occasional use on various bands then the power drops to about half with slider set to 100-again all bands show this when checked. Just today power dropped and I reset all cal points to default and power was reasonably close to 100w =\- 10 watts. Reset default is 50.5 vs. 56 it had been set for on 80 m. Several times in the past after redoing power cal for all bands manually to bring power back up to max I turn on and transmit to find power has doubled greatly exceeding rated power. (measures on 1 external reliable meter and and antenna tuner meter all feeding dummy load. I then recal. to get 100w and it lasts for some time. Using Astron RS70 with meters-it shows good voltage-about 13.8 and metering at radio power connector only drops .5 volt or less with 50-100w out. Ammeter on power supply seems to show appropriate current at higher or lower power level. I use same supply(separate 12 volt cable connected at power supply terminals for an Anan 8000 with no power cal issues when set for 200 watts.
Not seeming like a PTT relay contact issue or the like. Any thoughts on this? I have done database rests for other reasons but does not seem to matter.

Tom
KA1GXR