The text in the OPC UA Specification Errata 1.04.3 is suggesting an incompatible
change to the existing Stacks:

"The SequenceNumber shall start at 1 023 and monotonically increase for all
Messages and shall wrap around when it is equal to 4 294 966 271
(UInt32.MaxValue – 1 024). The first number after the wrap around shall be
1 023. Note that this requirement means that a SequenceNumber does not
reset when a new TokenId is issued. The SequenceNumber shall be
incremented by exactly one for each MessageChunk sent. For backward
compatibility, receivers shall accept SequenceNumbers less than 1 023 and
greater than 4 294 966 271 provided they are in sequence. Administrators
shall be able to disable this backward compatibility. Receivers shall log a
warning when a rollover does not conform to the current specification."

This implies the server send 4 294 966 271 --> 1 023

But that will not be accepted by the previous wording and I think .NET and
AnsiC stacks agree in requiring 4 294 966 271 --> 4 294 966 272 --> 1 023.

Previous wording was:

"The SequenceNumber shall also monotonically increase for all Messages and shall
not wrap around until it is greater than 4 294 966 271 (UInt32.MaxValue –1 024). The first number after
the wrap around shall be less than 1 024."
Therefor the check is "prevSequenceNumber > 4294966271 && nextSequenceNumber < 1024".

I am not sure if that is intentional, but if it is the sentence with "For backward compatibility..."
makes no sense since the other side will terminate the connection at this point anyway.