Currently, if a unit is respawning, there is a period of invulnerability that lasts for about a second. This period is indicated visually by your unit flashing in and out. While your unit is invulnerable, it passes through other units, cannot be killed, and will not phase back into the game (become vulnerable) if it is touching an enemy unit. If the unit is in contact with an enemy, the invulnerability period will persist until the two units are no longer in contact.
However, there is an exception to this rule:
When a Warrior is in the invulnerability state and interacts with an enemy-controlled Snail, the Warrior will immediately phase back in, killing the Snail-rider.
BumbleBear currently does not consider this a bug, but it is a unique interaction that is being closely examined for its impact in competitive and casual play. If you have any thoughts on this interaction and would like to share them with us, please contact support@bumblebeargames.com and let us know what you think!