AcuServer Issues?

Scenario in general:

We have a client with some unusual (at least for us) possible issues with AcuServer. At random times during a day the client's users will begin to throw  9D,103 and 9D, 104 error messages. The client has a work around of rebooting the server on a daily basis in the early AM hours. The client would prefer not to have to reboot the server. 

Specifics in regards to the client's setup and other observations:

The problem started approximately 4 weeks ago and to the client's knowledge no changes have been made to the environment. Our review would agree in regards to changes in the AcuCOBOL environment in the last 4 weeks but the client does apply Windows updates as released.

The client's entire infrastructure is virtualized using VDI for user workstations running Windows 7 and application server  Windows Server 2008.

The client has approximately 30 to 50 concurrent application users at any one time., 

The client has 9 instances of AcuServer running as a windows service on the application server. AcuServer only serves data files the runtime, cblconfi and objects are delivered to the client's users via a network share from the same server. The instances have been "loaded balanced" by distributing desktop shortcuts using different config files per client user . 

The errors being thrown by the client's users appears to be random in regards to the instance of AcuServer.

The client is running version 9.1.2 of the AcuCOBOL runtime with Acu4GL for MS SQL Server enabled. The client does not use the Acu4GL portion of the runtime. The runtime also has several patches applied.

AcuServer is version 9.0.0.

We couldn't find any windows application logs indicating AcuServer failure, AcuServer is not being started with the -e option.

The application makes use of a sequential file for an audit log of of date, time, user and COBOL object opened. The sequential file has not been truncated since 2002 and is now 811MB with about 8.5M rows. Basically each time a user opens a COBOL program a row is appended to the sequential file. 

The application also has a data file with 43M rows with 4 data file extents and 2 index file extents. The total size of the files is 17GB. 

Even though we are not the developers of the application we have several clients using the same application in a similar type of environment without issue. One difference is the version of AcuServer and runtime. We do not have another client with the same combination of runtime and AcuServer version. We also do not have another user with the same size of Vision file and sequential file mentioned above. 

The client's users throwing the errors are not always accessing the large Vision file noted above. All the user's clients access the large sequential file. 

Any suggestions or comments are appreciated.