You have several receive locations that use the MQSeries adapter in BizTalk Server. When there are many messages on a queue that must be read in order, the other MQSeries receive locations on the same BizTalk host instance stop receiving until all messages from the in-order receive location have been read.
Cumulative update information
This problem was fixed in the following cumulative updates for BizTalk Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about service pack and cumulative update list for BizTalk Server.
Learn about BizTalk Server hotfixes and cumulative update support.