Problem with S1 node XB24-DM VER. 8067

Hello,
I have in network two nodes: A transmitter, B receiver.
Node A sends every 1s a message with an acknowledgement
to node B.
After sending about 200 messages node A hangs, stops responding to uart and need to reset it. Node B still works.

When I changed node A to S1 PRO XBP24-DM module VER. 8062 all is ok, it worked all night.

Do you have any ideas what is going on?

Thanks.

What firmware version were you using before?

XB24-DM VER. 8067

One more thing: when we flashed this S1 with older soft (the same which S1 pro already had - 8062) all is also stable.
Thanks.

What happens when you flash them with the Point to point 802.15.4 code on them? Why are you using Mesh for a point to point connection? Are you using hardware flow control at all?

Hi,
actually we test only two nodes but final project has about 1000-2000 nodes in one network. Yes we have hardware flow control.
Thanks.

Do you see this issue when you use Unicast addressing over the default broadcast?