Rolling file appender with 'maxSizeRollBackups' set to a positive number tries to initialise by looking at existing log files to continue the rolling sequence and set 'm_curSizeRollBackups' to its correct value but the base filename format is wrong.
In method GetWildcardPatternForFile with m_preserveLogFileNameExtension true it should construct a wildcard pattern but the 'baseFileName' is not enough to fully identify the log file when 'datePattern' is also specified.
For example: -
With log files such as: -
the pattern created is 'MyLogFile.*.log'
The date pattern is missing and as a result no log files are found and historical log files get overwritten rather than rolled over.
A quick fix I'm using is to remove the '.' from the literal ".*" in the wildcard. This allows the OS to identify the log files. Later code makes a fuller check of the exact log file format and therefore this may be safe but I would think it needs more validation and testing to be sure this works under all circumstances.