[mufcfan]

I have the same issue. I have tried everything to fix it without re-installing. Even deleting the OOTP 23 folders from AppData and Documents would not help.
A reinstall did help but after one or two simulations the issue is back and I can't submit changes.

Username, team, league:
mufcfan
Budapest Red Devils
Lambda Tau

The debug file shows the same errors for me too.

2022-05-01 10:48:14 get_http_object: Successfully created HTTP object. Max connections: 10
2022-05-01 10:48:14 clear_download_tasks: Cleared download tasks list. Closed 0 tasks.
2022-05-01 10:48:15 APP_FRAMEWORK::pt_submit_team: Called with get_request_pt_submit=0, quiet=0 and include graphics=1
2022-05-01 10:48:15 pt_export_team_graphics: Uploaded file with HTTP response status: 200 - E:\<username>\Documents\Out of the Park Developments\OOTP Baseball 23\saved_games\7ea000000000000000000042.pt\import_export\team_graphics.zip , team id: 1912
2022-05-01 10:48:15 pt_export_team_graphics: Server returned: 
teamgraphicsupload4
Array
(
    [data] => Array
        (
            [name] => team_graphics.zip
            [type] => application/zip
            [tmp_name] => /tmp/phpPKCf0L
            [error] => 0
            [size] => 10326
        )

)
UPLOAD_FAILED
2022-05-01 10:48:15 upper_area_page - pt response: setPTTeamData
2022-05-01 10:48:15 upper_area_page - pt response cleared: setPTTeamData
2022-05-01 10:48:16 ClientListener_OnError: message: http: request body too large
2022-05-01 10:48:16 upper_area_page - pt response: getPTUserStatus
2022-05-01 10:48:16 upper_area_page - pt response cleared: getPTUserStatus
2022-05-01 10:48:16 upper_area_page - pt response: getPTInfo
2022-05-01 10:48:16 upper_area_page - pt response cleared: getPTInfo
2022-05-01 10:48:16 get_http_object: Successfully created HTTP object. Max connections: 10
2022-05-01 10:48:16 clear_download_tasks: Cleared download tasks list. Closed 0 tasks.
2022-05-01 10:48:20 APP_FRAMEWORK::pt_submit_team: Called with get_request_pt_submit=0, quiet=0 and include graphics=1
2022-05-01 10:48:20 APP_FRAMEWORK::pt_submit_team: Skipped setPTTeamData because no data was changed
2022-05-01 10:48:20 ClientListener_OnError: message: http: request body too large
2022-05-01 10:48:22 get_http_object: Successfully created HTTP object. Max connections: 10
2022-05-01 10:48:22 clear_download_tasks: Cleared download tasks list. Closed 0 tasks.
2022-05-01 10:48:58 get_http_object: Successfully created HTTP object. Max connections: 10
2022-05-01 10:48:58 clear_download_tasks: Cleared download tasks list. Closed 0 tasks.
2022-05-01 10:49:03 APP_FRAMEWORK::pt_submit_team: Called with get_request_pt_submit=0, quiet=0 and include graphics=1
2022-05-01 10:49:03 APP_FRAMEWORK::pt_submit_team: Skipped setPTTeamData because no data was changed
2022-05-01 10:49:04 ClientListener_OnError: message: http: request body too large