Replication/Broker problems

Starting a new thread to make it easier to track what's going on. 

Progress 11.2.1 on 32 bit Windows Server 2003. (I know!) 

Running Replication Plus. The source is in normal processing:

Database is enabled as OpenEdge Replication:  Source

Server is:                                  In Normal Processing
Number of configured agents:                1
Delay Interval (current / min / max):       220 / 5 / 500
Recovery information:
    State:                                  No recovery being performed
    Agents needing recovery:                0
    Agents connected:                       0
    Agents in synchronization:              0
Transition information:
    Type:                                   Manual

As is the Target:

Database is enabled as OpenEdge Replication:  Target

Agent:
    Name:                                   agent1
    ID:                                     1
    Host name:                              192.168.125.1
    State:                                  Normal Processing
    Ready:                                  Yes
    Critical:                               No
    Method:                                 Asynchronous
Agent is waiting for:                       Nothing
Maximum bytes in TCP/IP message:            8512
Server/Agent connection time:               Tue Dec 23 20:28:20 2014
Delay Interval (current / min / max):       90 / 5 / 500
Transition information:
    Type:                                   Manual
The last block received at:                 Wed Dec 24 08:06:56 2014
Activity information:
    Blocks received:                        119647
    Blocks processed:                       119647

On the source Database though I had a couple of 1890 errors this morning (not sure what for as I couldn't reconcile it to a process). More importantly the AI files aren't being unlocked and emptied. 

Actually looking again, it seems it's unlocking some, but they're filling up faster than it can unlock them. 

[2014/12/24@08:00:21.544+0000] P-11828      T-11840 I RPLS  215: (11805) Unlocking after-image file 5432 and locking ALL FULL after-image files beginning with file 5433. 
[2014/12/24@08:00:25.366+0000] P-7544       T-1636  I AIMGT 163: (3789)  Marked after-image extent H:\AIFILES\LIVE\icmasliv.a104 EMPTY. 

Any ideas what to look at? Not come across this sort of problem before and my knowledge is somewhat lacking.