set_pev(Client, pev_health, Health + float(NeededHealth));
-> the next round, player spawn with 0hp, the camera is on the ground (like u just died) and you can't do anything even with our code
set_user_health(Client, Health + NeededHealth);
and
fm_set_user_health(Client, Health + NeededHealth);
-> player dies after respawn when he was killed (e.g. by slay/slap/napalm nade). But they respawn immediately and everything is normal
Both while regeneration was activ the round before and they were killed.