Why would a guy come back every like 5 months if he’s so inconsistent and unreliable?

We haven’t properly spoken since last year. I blocked him then came back a few weeks later, then realised he is definitely unreliable and blocked him again. 3 months or so he calls (different number). 5 months later he calls again and sends me a message. What is that about
Why would a guy come back every like 5 months if he’s so inconsistent and unreliable?
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