Is this guy a red flag or just sensitive he gets angry for replying late?

A guy whom I used to work at office likes me, but he hasn't directly told me how he feels. He often flirts and asks about my future marriage plans. Sometimes he wants to open

up but is afraid I'll reject him. When I take time to respond, he does the

same. Recently, I was in the hospital, and he asked where I was.

I told him, and he showed concern, asking about my health and expressed how much he cares. But when I responded late the next day by telling I'm sorry for responding late as I was sleeping till evening after coming back tired from the hospital and then got busy by doing online office work as I'm on leave , he just said "ok np" without showing much care. This has happened >many times -despite explaining him my situation for being busy he gets upset when I don't respond quickly, even though I've explained I can't always be available. I've told him our different chat schedules shouldn't affect our friendship, like my other friends. He sometimes starts conversations but not often if I don't initiate chatting also he has admitted to having anger issues. Is he a red flag or just sensitive?

Is this guy a red flag or just sensitive he gets angry for replying late?
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