Today I flashed one of my BV6300 to the latest ROM (BV6300Pro_EEA_TE988_V1.0_20200909V15) because I was facing problems with the WiFi connection that randomly disconnected in short periods of time (30 seconds - 5 minutes). Sometimes it reconnects, sometimes it stays offline. In addition to installing the new ROM, I did 4 factory resets and only activated WLAN. I tested the Wifi connection with a sim card installed and without. There are to WLAN AP in the house, using the same SSID + password. 
What's strange about the BlackView compared to all other WiFi devices I use is, that it displays each access point in the list of available APs. So two times the same SSID is shown. Once you've  connected manually to both of them (you need to authenticate on each AP even though SSID an password are the same on the APs), suddenly both of the listed SSIDs are showing the same signal strength (number of bars are the same).
Mi first BV6300 is still on the V14 ROM and keeps connected (what the new device does neither with V14 nor with V15), but it lists the two APs separately, too. I did some tests with both phones and noticed that they don't switch automatically to the AP with that is closer to the pone, when you change your position in the house. Only switching off and on the WiFi are forcing a switch to the better AP.
I compared the settings of both phones, the one loosing the connection has the same settings as the one that stays online.

So I think it is a hardware problem on the second device. And a bad WiFi driver that needs some improvements on both devices.
A related topic seems to be described here: https://bbs.blackview.hk/viewtopic.php?f=310&t=542145&p=989075&hilit=wifi#p989075

1. Any ideas how to fix the problem?
2. Is a new ROM planned for the BV6003 fixing this bug (and maybe in addition updates to android 11) ?