Strange error in SQL Server Reporting Services, EventID 108 - sql-server

Question

I am using SQL Server 2019 (15.0.1102.861) reporting services. From time to time it fires an error multiple (5-6) times within the same second. There is nothing special that happens at this time, no subscription or any scheduled task or anything else, but of course I can't say if anyone is just opening a report with a - let's say "unoptimal" - query or is trying to edit a report and runs into something. There is no regularity in any way.
In Windows event log it reads:
error, ID:108, Source:Report Server (SSRS), Message:Report Server (SSRS)
There is no more information, except the word DAX, but I am quite sure that no one uses Data Analysis Expressions (as Analysis Server is not installed, but maybe Skype for Business or Anywhere 365 uses such a thing for the reports and cause this error - could that be the reason?):
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Report Server (SSRS)" />
<EventID Qualifiers="0">108</EventID>
<Level>2</Level>
<Task>2</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2023-02-08T06:26:17.553286000Z" />
<EventRecordID>365647</EventRecordID>
<Channel>Application</Channel>
<Computer>MyReportServer.MyDomain</Computer>
<Security />
</System>
<EventData>
<Data>Report Server (SSRS)</Data>
<Data>DAX</Data>
</EventData>
</Event>
Just to demonstrate the interval it happens, these are the timestamps for the whole series:
<TimeCreated SystemTime="2023-02-08T06:26:17.553286000Z" />
<TimeCreated SystemTime="2023-02-08T06:26:17.553286000Z" />
<TimeCreated SystemTime="2023-02-08T06:26:17.537658500Z" />
<TimeCreated SystemTime="2023-02-08T06:26:17.522032200Z" />
<TimeCreated SystemTime="2023-02-08T06:26:17.037601300Z" />
In the Reporting Service log file I find two warnings during this time, and I don't think they have anything to do with the error above, but just to be complete:
2023-02-08 06:26:13.7997|INFO|21|Deleting expired log file: C:\Program Files\Microsoft SQL Server Reporting Services\SSRS\LogFiles\RSPortal_2023_01_04_19_15_05.log Last written: 04.01.2023 19:15:05
2023-02-08 06:26:13.7997|WARN|21|Exception deleting expired log fileSystem.IO.IOException: The process cannot access the file 'C:\Program Files\Microsoft SQL Server Reporting Services\SSRS\LogFiles\RSPortal_2023_01_04_19_15_05.log' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalDelete(String path, Boolean checkHost)
at Microsoft.BIServer.HostingEnvironment.Logger.DeleteExpiredFilesInternal(Int32 keepUntilDays, FileInfo[] logFiles)
2023-02-08 06:26:23.8306|INFO|21|Deleting expired log file: C:\Program Files\Microsoft SQL Server Reporting Services\SSRS\LogFiles\RSPortal_2023_01_04_19_15_05.log Last written: 04.01.2023 19:15:05
2023-02-08 06:26:23.8306|WARN|21|Exception deleting expired log fileSystem.IO.IOException: The process cannot access the file 'C:\Program Files\Microsoft SQL Server Reporting Services\SSRS\LogFiles\RSPortal_2023_01_04_19_15_05.log' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.File.InternalDelete(String path, Boolean checkHost)
at Microsoft.BIServer.HostingEnvironment.Logger.DeleteExpiredFilesInternal(Int32 keepUntilDays, FileInfo[] logFiles)