Casa C3200 stops BGP advertisement after uplink dc/c.

Hello,

We have +30 Casa C3200 running at different sites, and they are (through a different ISP) connected with BGP in a VPN (full mesh) network.
Two other sites where we have core routers are also connected to the VPN (to provide the internet access).

The issue we've been having is rather strange, and i wonder if anyone else use the Casa C3200 with BGP (or done in the past), and have experience with the following issue?

The problem occurs when the ISP does service maintenance (for example, SW update on a switch, their CPE, PE router etc).
In other words, the connection goes down for somewhere 5-20 minutes.

What happens is; when the connection comes back up, the Casa connects to it's BGP neighbour and everything seems fine. physical connection OK, BGP session is up and running etc.
Except, the Casa no longer advertises any prefixes. The Casa does however receive prefixes properly.
The problem does not occur every time a service maintenance is done, and it does not occur on specific C3200. In other words it seems quite random.

The only solution we've found so far is to remove the prefixes from routing instance (router bgp ASxxx) address-family ipv4 unicast list, and then adding them again.
After doing this everything starts working in a couple of seconds.
However I'm looking for a more permanent fix then this.

Configuration of the C3200's is nearly identical, except for the obvious differences (linknets, CM and customer prefixes etc).

host#show system
Product: C3200, Module: SMM
Major rev 1, Minor rev 3
serial_no = x
CFE version 2.1.5

host#show version
Running Image: SMM Rel 6.1.5, Ver 2,build6249, Fri Feb 9 11:04:10 EST 2018,(relmgr)
Configured boot device: flash2
flash1: SMM Rel 6.1.5, Ver 2,build5ca2, Wed Dec 20 20:01:18 EST 2017, ( relmgr)
flash2: SMM Rel 6.1.5, Ver 2,build6249, Fri Feb 9 12:26:16 EST 2018, ( relmgr)
CFE Boot: Major 2, Minor 1, Build 5

And the current config for BGP (changed public IP's to bogus prefixes etc):

ip prefix-list BGP-in description "BGP-Filter_received_routes"
ip prefix-list BGP-in seq 1 permit 0.0.0.0/0
ip prefix-list BGP-in seq 15 deny 10.0.0.0/8 le 32
ip prefix-list BGP-in seq 20 deny 172.16.0.0/12 le 32
ip prefix-list BGP-in seq 25 deny 192.168.0.0/16 le 32
ip prefix-list BGP-in seq 30 deny 1.1.1.0/24 le 32
ip prefix-list BGP-in seq 35 deny 2.2.2.0/26 le 32
ip prefix-list BGP-in seq 100 permit any
ip prefix-list BGP-out description "BGP-Filter_advertised_routes"
ip prefix-list BGP-out seq 5 permit 10.20.145.56/30
ip prefix-list BGP-out seq 10 permit 10.20.24.0/23
ip prefix-list BGP-out seq 15 permit 1.1.1.0/25
ip prefix-list BGP-out seq 16 permit 1.1.1.128/25
ip prefix-list BGP-out seq 20 permit 2.2.2.0/26
ip prefix-list BGP-out seq 100 deny any

router bgp *snip*
no synchronization
bgp router-id 172.16.63.58
neighbor 172.16.63.57 remote-as *snip*
neighbor 172.16.63.57 password *snip*
!
address-family ipv4 unicast
network 10.20.24.0 mask 255.255.254.0 <---- CM prefix
network 1.1.1.0 mask 255.255.255.128 <---- customer prefix
network 1.1.1.128 mask 255.255.255.128 <---- customer prefix
network 2.2.2.0 mask 255.255.255.192 <---- customer prefix
network 10.20.145.56 mask 255.255.255.252 <---- GIADDR prefix for CM & customer in IP-bundle interface
neighbor 172.16.63.57 activate
neighbor 172.16.63.57 prefix-list BGP-in in
neighbor 172.16.63.57 prefix-list BGP-out out
exit-address-family
!

Does anyone have any experience with this, or any ideas as to what it causing this?
We see no errors in logfiles etc, so we are quite lost as to why this happens.

Thanks in advance