If the vpn is allowing access to the OS for other functions and does not happen to have a ‘really small’ data restriction placed on it (something not common in a standard setup) then you do not have a vpn problem. It sounds as though you have the same issue others are having in the firmware.
I have been working on the issue and converted the log write functions to use sprintf instead of the current method of appending. It seems to fix the issue. A bit more testing and I should know what kind of success it provides. It seems as though the current logs are somehow overrunning any buffered space provided for them. Essentially using to much ram during the read or write processes, and causing the MCU to reset.