cannot pair bluetooth

Hi! I've a mi5 64 and a Midland BT next (is an intercom I use when I go in bike). With all my old phones I could pair the Midland without problem, in a minute, but with Mi5 is impossible! the phone prompts for the code (0000) and seems that connect but finally the status is: connected (no device). An strange error, no? I don't know how can I solve this problem, some idea here?

The intercom is very expensive and it's not my idea to buy another! :laugh:

Thanks!
Jordi

ps: I've tried the stock rom when I bought and now I've the xiaomi.eu dev 6.4.21 .

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