I found a bug.
ProtocolFilters supports generating debug logs.
To generate the log replace ProtocolFilters.dll with a version from
Release_c_api_logs or Release_logs (depending on C or C++ API is used)
and reproduce the problem.
C# and Delphi wrappers use ProtocolFilters with C API.
The debug log will be written to ProtocolFiltersLog.txt in the same folder with executable. Send it with a description of the issue to firstname.lastname@example.org.
The debug build starts writing log automatically. It is possible to start and stop writing the logs using API functions pf_startLog/pf_stopLog,
for example to save several log files and control their size.