Yes, it looks like a pressure-balancing is needed, after setting the circulating pump to maximum speed. ( but the actual bleeding should be done with the pump not operating, as it is possible to let air into the system.)
this once happened to me what i did was to turn all other radiators off apart from one with the problem, bleed the air out of rad, and turned on the c/h ,i let it run for while until was nice and toasty then gradually went round and opened other rad valves , seemed to work for me
good luck :D
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