GA SMA LOST VOR NAVIGATION CAPABILITY WHEN IN CLOUDS. ZME GAVE VECTORS BACK TO DEP ARPT.

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FLT IN VMC PRIOR TO DSNDING INTO APPROX 3500' THICK CLOUD LAYER. IDENT CONFIRMED ON PGO ON CHANGEOVER FROM FSM. UPON ENTERING CLOUDS CLOSE TO PGO VOR STARTED SMALL SCALLOP. BELIEVING TO BE IN CONE OF AMBIGUITY CONTINUED ON HDG. ZME ASKED IF TURN HAD BEEN STARTED. I REPLIED WAITING FOR FLAG TO SWITCH. ZME THEN SAID THEY HAD ME 5 MI S OF PGO. I THEN ASKED FOR VECTOR TO INTERCEPT APCH COURSE. PRIOR TO INTERCEPT I TRY TO FIND WHY I OVERFLEW PGO. ON INTERCEPT I USED BOTH NAVS TO TRACK OUT ON 105 DEG R. UPON REACHING APPROX 3000' MSL; BTWN LAYERS; NAVS WORKED PERFECT. AT END OF APCH BACK INTO CLOUDS NAVS SCALLOPED AGAIN. UPON EXECUTING A MISSED APCH AT 5000' MSL I ASKED FOR VECTORS TO FSM. IN CLEAR (OUT OF CLOUDS) FSM IN IDENTED AND SEEMS TO WORK PERFECT. NO FURTHER PROB TO LNDG. CONTRIBUTING FACTORS: MY COMPLACENCY AND INDECISION LET THINGS GO AS FAR AS THEY DID. ALSO; AFTER TALKING WITH AN AVIONICS TECHNICIAN IT WAS BROUGHT UP THAT MAYBE AN INTERMITTENT BAD BOND ON A SURFACE COULD CAUSE SOME SORT OF STATIC BUILDUP. THIS HAPPENED ONCE VERY SHORTLIVED OVER A YR AGO AND HAS NOT DONE SO SINCE UNTIL THIS INCIDENT.