Part 6, 5.2.2.17, Table 17 says the following about the encoding mask of DataValue types:

0x01 False if the Value is Null.
0x02 False if the StatusCode is Good.
0x04 False if the Source Timestamp is DateTime.MinValue.
0x08 False if the Server Timestamp is DateTime.MinValue.
0x10 False if the Source Picoseconds is 0.
0x20 False if the Server Picoseconds is 0.

In applications that care about picoseconds (e.g. physics), there is a big difference between
not measuring picoseconds at all
and
having measured zero picoseconds.
But this difference is lost in the encoding.

This has come up since it was proposed to "throw out" picosecond information in our encoder if zero picoseconds are measured.
https://github.com/open62541/open62541/pull/2534
In accordance with the current spec we would have to do this.

As a solution, we propose the following change to table 17:

0x01 False if the Value is Null.
0x02 False if the StatusCode is Good.
0x04 False if no Source Timestamp is defined.
0x08 False if no Server Timestamp is defined.
0x10 False if no Source Picoseconds is defined.
0x20 False if no Server Picoseconds is defined.

Should be 100% compatible with the existing decoders.