246 Failed to execute IO operation 'Open'.

I have ACRONIS VMPROTECT virtual appliance installed and the vCenter appliance backup throws this error message every time the backup job runs. Please advise (there are a couple of other posts on here with the same error message that have gone unanswered maybe this one will)

Failed to execute IO operation 'Open'.
Additional info:
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Error code: 246
Module: 83
LineInfo: c61573f663f5d800
Fields:
Message: Failed to execute IO operation 'Open'.
--------------------
Error code: 208
Module: 83
LineInfo: c61573f663f5d756
Fields: code : 15
Message: VMware_VDDK: The file is already in use
--------------------