new-moverequest from Exchange 07 to 13 throws completed with warning

Hi, 

I am new to this forum, but thought to try it out. I have set up a lab environment with a 2012 dc in domain a together with a dag exchange system of 2 servers with all roles installed on each exchange server. The exchange servers are 2013. 

I have a domain b with a 2012 domain controller - and a 2008r2 server with 2007 exchange installed (sp3). 

I have trusts setup between the two, and I am trying to do a cross migration of some test accounts. I've successfully moved all items - however when I look at the output from the command.

get-moverequeststatistics -identity test1 | fl

it states : 

Message : Warning: The following failure occurred after the active directory modification completed: couldn't find database "LABEX07\First Storage Group\Mailbox Database". Make sure you have it typed correctly.

The database it says it can't find is from the source 2007 exchange server - and I know it exists. I can't see anything else wrong with the content of whats moved to the 2012 domain except for that message. Does anyone have an idea of what it means? My movement code was

.\prepare-moverequest.ps1 -identity test1@domainb.local -remoteforestdomaincontroller dc01.domainb.local -remoteforestcredential $remoteuser -localforestdomaincontroller dc01.domaina.local -localforestcredential $localuser

followed by the new-moverequest 

new-moverequest -identity test1 -remoteLegacy -remotecredential $remoteuser -remoteglobalcatalog dc.domainb.local -targetdatabase 'mailbox db 1' -targetdeliverydomain domaina.local