Unable to connect to SSH-2.0-dropbear_2020.80 since WinSCP 6.3.7

I've been unable to connect to SSH-2.0-dropbear_2020.80 since WinSCP 6.3.7 - this is running on a modified Huawei router. Every version since 6.3.7 fails. I've tried modifying several settings in the connection config to get it working, but I'm not an SSH expert.

Attached are a log of a successful connection using 6.3.7, followed by a failed connection attempt using 6.5.6.

Hoping someone can point me in the right direction as I'd rather use the latest version of WinSCP.