Broadlink RM mini 3: it transmits codes but cannot learn then anymore

Hi, I’ve got Broadlink RM mini 3 few months ago, I learnt TV on and off commands with it and have been switching TV on/off happily since then. It is still working fine, but today I tried to learn a new command (“source” button), but calling switch.broadlink_learn_command_192_168_1_12 service consistently leads to “Failed to connect to device” error in, and no code is learnt.
Any help is appriciated!
Using HA 0.90.1 in installation.