when a new host join an existing pool, it starts by configuring the management interface. so the first bound created is the management one (as bond0) even if the master of the pool has it as bond1.

while doing some tests with 8.3 I got problems too, but not systematically (as you, it seems).

I will send to you a PM regarding xensource.log

@afmart_dei could you share the /var/log/xensource.log of the joining host ? ideally the whole part after the host started (you could look at the file before rebooting and strip all lines before the last line you saw)