trying to broadcast offline signed transaction, but got this error "The transaction was rejected by network rules. (16: mandatory-script-verify-flag-failed (Script failed an OP_WQUALVERIFY operation))". Electrum 2.8.3
Did you copy and paste that error? or type it in manually... because it should be OP_
EQUALVERIFY.... not OP_WQUALVERIFY

If it was copy/paste... Did you accidentally modify one of the transaction files while you were moving things around?
It was typed manually and should be "E" instead of "W" - can't directly copy/paste this Windows error message. Can't imagine any possibility when the transaction file could be modified. It was saved on pendrive directly from Electrum wallet (not by copy/paste).