After an initial test, I am able to reproduce the issue as you mentioned by using your template XLSX file. I found TEXTJOIN() function results are inconsistent with MS Excel.
We require thorough evaluation of the issue. We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.
Issue ID(s): CELLSJAVA-46105
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@TarasTielkes
We are pleased to inform you that your issue has been resolved. The fix will be included in our upcoming release (Aspose.Cells for Java v24.9) that we plan to release in the first half of September 2024. You will be notified when the next version is released.