The reset of flag is not correct for the OP_NEXTCHNL part.

[ngraziano]

It can be removed in the current source but I think that it should be set after like in line 2075 (LMIC_setSession).

[terrillmoore]

I think I agree. The OP_NEXTCHNL handling stuff is complex, but it is clear that that the following is true:

1. if you're (re)joining, OP_NEXTCHNL should always be reset. (There are ASSERT()s in the various bandplans in the join engine that this must be so.)

2. it's only sensed here:

   arduino-lmic/src/lmic/lmic.c

   Lines 1805 to 1810 in 2f6cabe

   	if( (LMIC.opmode & OP_NEXTCHNL) != 0 ) {
   	txbeg = LMIC.txend = LMICbandplan_nextTx(now);
   	LMIC.opmode &= ~OP_NEXTCHNL;
   	} else {
   	txbeg = LMIC.txend;
   	}

   .

This line is right after a successful join-accept, and it will cause the next non-join tx to choose a new channel.