Is the route table you are checking peered to both the exchange and inet peer directly or does it learn the full table routes from a separate bgp neighbor?
And if so, is that iBGP or eBGP between these peers and the topology?
Basically, I would follow the path for the /21 route in the internal network by peer.
Confirm this enters from the expected peer
show route receive-protocol bgp 10.1.1.1 | match 10.10.10.0/21
Confirm added to the active table
show route protocol bgp 10.10.10.0/21
confirm it is then advertised to the next peer internally
show route advertising-protocol bgp 10.1.1.2 | match 10.10.10.0/21
and then on the peer 10.1.1.2 for the check on receive to see if it accepts this prefix
and so on until arriving on the peer in question