I have rework the internal Action 0 property system for TTDPatch and plan to commit the changes in the TTDPatch trunk branch the following week.
What does this mean as grf author / player ?
Revisions after around r1893 may fail with sprite errors because the new internal system has an unknown bug or the old parser simply ignored something in your grf.
The first test with DBSetXL and stations didn't show any problems.
You may want to test an old nightly http://nightly.ttdpatch.net/ then.
Bridge GRFs may fail. (see below for more)
What changes are done? Why changes in newgrfs core algorithm are done?
Action0 in it's current system manages internal 3 separate ways to set properties for a id. Currently we lose 8 properties for any non vehicle.
Neither is the current system flexible enough to replace these with custom internal function handlers to keep grf compatibility when the internal may change in the future. New features may be more logical structured
Old features are mostly impossible to extend id wise.
Lot of special code handling but less memory usage by definition.
New System:
Uses more memory to define the properties, but is a lot easier to maintain and can be extended, a lot code paths are removed and replaced by table lookups.
As the bridge Action0 was quite a hack, it couldn't be converted.
The result was a rewrite of the current bridge functions. While I haven't managed to fix the gui and add new stuff. The internal system now allows theoretical new 100 bridge ids.

Therefor some new stuff needs to be introduced property wise. (New icon handling, text handling, fail back handling) so the bridge grfs may fail... (As a grf author may want to add your wishes for bridge properties here)
Note: If you have currently errors with sprites with r1893, or sprite errors in beta it's not my fault.