GL-AR750 QoS upload speed limit not working - a bug?

Within the GL-AR750 Admin Panel, in the Clients connected you can set QoS upload and download speed limits. The download speed works as expected but the upload speed limit has no effect on the client? Is this a bug?

GL-AR750 software version 3.027 - Compile time 2019-10-09 20:00:36

Using 3.104 firmware and tested on cable. Limiting speed to 1MByte/s and it worked.

3.104 can be download from GL.iNet download center

Does not work when connected GL-AR750 via wifi to internet and then clients to GL-AR750 also on WiFi.