SSH port forward: Unsupported or unrecognized SSL message

I am trying to set up a dynamic port forwarding, using the "SSH port forward" connection type, but when sending requests to an API on the remote end, I get the following message.

An exception occurred while attempting to connect to: https://user-mgmt.nbi.welktx08vzwvnom-y-nk-ems-00.vcp.vzwnet.com/auth/realms/NEO/protocol/openid-connect/token
The exception was: 
Unsupported or unrecognized SSL message
Root cause: 
SSLException: Unsupported or unrecognized SSL message

I enabled verbose logging on the connection, and these are the messages I am seeing at the same time.

[8/31/2021 5:34:19 AM] Sending forward channel open request: 2/- user-mgmt.nbi.welktx08vzwvnom-y-nk-ems-00.vcp.vzwnet.com:443
[8/31/2021 5:34:20 AM] Received channel open confirmation: 2/2 WS 200000/2097152 MPS 32000/32768
[8/31/2021 5:34:20 AM] Successfully established connection localhost:9081 -> user-mgmt.nbi.welktx08vzwvnom-y-nk-ems-00.vcp.vzwnet.com:443
[(-549455608) Unknown error.]
[8/31/2021 5:34:20 AM] Sending channel EOF: 2/2
[8/31/2021 5:34:20 AM] Sending forward channel open request: 3/- user-mgmt.nbi.welktx08vzwvnom-y-nk-ems-00.vcp.vzwnet.com:443
[8/31/2021 5:34:20 AM] Error writing to local end of tunnel
[(10053L) An established connection was aborted by the software in your host machine.]
[8/31/2021 5:34:20 AM] Sending channel close request: 2/2
[8/31/2021 5:34:20 AM] Received channel close request: 2/2
[8/31/2021 5:34:20 AM] Channel is closed: 2/2

When setting up the same tunnel with Putty, it works as expected.

Is there a setting I perhaps overlooked?

BTW, it works as expected with the MacOS version of RDM.

Thanks in advance!