I have recently installed a R600VPN router V4. Upon installation I upgraded to the latest firmware, 4.0.4 Build 20200313. 

Everthing works very well but I noticed that the system log only lasts for four days of entries. Entries older than four days are not displayed.

I tried saving the log, to see if it was just a display problem but it isn't, the log entries have actually been deleted.

I previously used a R470T+ router and the system log on that router contained many weeks worth of entries.

Is this a feature of the R600VPN router or perhaps a bug ?

Thank you.