Dear Arjan,
Please see note 1814918 in relation to the error message that you have described.
In order to clarify this issue, please note that the corrections from note 1814918 are already present in your system. The error was precisely created with the implementation of note 1814918 in your system after the upgrade. In your case, the following section of the note is relevant for you.
"WHAT_TO_DO" section: Check whether you really use the ledger with the pooled table. Often, the ledger L0 for pooled table GLT1 delivered by SAP is updated without actually being used or valuated. Bear in mind that updating this type of ledger unnecessarily costs both performance and memory space. If the ledger is no longer required, deactivate it with Customizing transaction GCL2. To do so, select the ledger and first delete all activity assignments (both assignments directly to the ledger and assignments to the ledger/company code or ledger/company combination). Then deactivate the 'Ledger Posting Allowed' indicator in 'Additional Settings' on the ledger master data screen. From now on, the ledger will not be posted.
If the ledger for the pooled table is still required, convert to a transparent table as soon as possible by implementing SAP Note 1014076. In the exceptional case that you still want to use the ledger with the pooled table and no longer want to see this information message when posting, you can deactivate message GI128 with transaction OBA5 by making a corresponding entry in table T100C."
Please follow the above steps which should solve your issue.
Best regards,
Cathal Conneely