connecting at the same time with mqtt3 and mqtt5 to the same broker does not work

[justme-1968]

this is probably not relevant 'in the real world' but during some testing of my client i noticed that connecting from the client at the same time with mqtt3 and mqtt5 to the same broker does not work.

only the last connection will receive messages as expected. the other one will result in an empty topic with the expected payload.