Michael Gale, your issue is different to the OP's one. The routes the OP has entered are all CIDR notable, he even uses CIDR when entering them via command line.
So please report a new bug, showing which routes you have entered and how they end up in /etc/NetworkManager/system-connections.
In addition, you could report a bug upstream, suggesting to let the rutes be saved in /etc/NetworkManager/system-connections in dotted-quad notation if they cannot be represented in CIDR notation.
Michael Gale, your issue is different to the OP's one. The routes the OP has entered are all CIDR notable, he even uses CIDR when entering them via command line.
So please report a new bug, showing which routes you have entered and how they end up in /etc/NetworkMan ager/system- connections.
In addition, you could report a bug upstream, suggesting to let the rutes be saved in /etc/NetworkMan ager/system- connections in dotted-quad notation if they cannot be represented in CIDR notation.