Failed to run a 60.00 timer in 'TimedPermissions v1.5.0' (InvalidOperationException: Collection was modified; enumeration operation may not execute.)
at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <437ba245d8404784b9fbab9b439ac908>:0
at Oxide.Plugins.TimedPermissions.m__0 () [0x0001e] in <6d2aead2170b431f88d9bc41b4bc7a96>:0
at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in :0

Failed to run a 60.00 timer in 'TimedPermissions v1.5.0' (InvalidOperationException: Collection was modified; enumeration operation may not execute.)
at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <437ba245d8404784b9fbab9b439ac908>:0
at Oxide.Plugins.TimedPermissions.<Loaded>m__0 () [0x0001e] in <57c669de7e664d97bdf65263b614cbd4>:0
at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in <ac41dd3599754d448b8c218b34645820>:0

Failed to run a 60.00 timer in 'TimedPermissions v1.5.0' (InvalidOperationException: Collection was modified; enumeration operation may not execute.)
at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <437ba245d8404784b9fbab9b439ac908>:0
at Oxide.Plugins.TimedPermissions.<Loaded>m__0 () [0x0001e] in <8ff32afb70964852b07fb9d146fb1412>:0
at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in <ac41dd3599754d448b8c218b34645820>:0

when restarting the server

same error

Failed to run a 60.00 timer in 'TimedPermissions v1.5.0' (InvalidOperationException: Collection was modified; enumeration operation may not execute.)
at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <437ba245d8404784b9fbab9b439ac908>:0
at Oxide.Plugins.TimedPermissions.<Loaded>m__0 () [0x0001e] in <8ff32afb70964852b07fb9d146fb1412>:0
at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in <ac41dd3599754d448b8c218b34645820>:0

My console throws these errors as well. Also, my players do not seem to be removed from their groups after the specified time, for example:

/addgroup player group 0d0h5m

They are added to the data file without issue, but the plugin seems to leave most players with groups/permissions that have already expired. I can find no obvious cause for this to happen, as things seem to be set up correctly. Maybe the two situations are connected?

Failed to run a 60.00 timer in 'TimedPermissions v1.5.0' (InvalidOperationException: Collection was modified; enumeration operation may not execute.)
at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <437ba245d8404784b9fbab9b439ac908>:0
at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <437ba245d8404784b9fbab9b439ac908>:0
at Oxide.Plugins.TimedPermissions.<Loaded>m__0 () [0x0001e] in <06542e71141d4c2b89eb390ecb00416d>:0
at Oxide.Core.Libraries.Timer+TimerInstance.FireCallback () [0x00018] in <ac41dd3599754d448b8c218b34645820>:0
(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 35)

MeinRust

The v1.4.0 works fine for us now .. the error is due to the version v1.5.0.

Awesome. Thanks a lot @MeinRust. It turns out that was exactly the source of all the issues. I have temporarily switched back to 1.4.0 while this is worked on and patched. Things seem to function as expected using the previous version, near as I can tell. Much obliged for the quick advice. Cheers my friend! <3