Describe the bug
If I put the option respawnOnDeath = false in the config file and restart the server, de player companion after the dead can respawn with the player companions item.

To Reproduce
tamed a slime (for example)
kill the tamed companion with lava or water
after the dead, right click with the tamed player companion item in anywhere
the tamed companion spawn after the dead

Debugging

[17:18:57] [Server thread/INFO] [Bo's Player Companions/]: Spawn 076a81b0-07d2-430b-a042-84afb45177ba BlockPos{x=-411, y=15, z=878} ServerPlayer['Wally720'/354, l='ServerLevel[world]', x=-408.09, y=16.48, z=878.52] ServerLevel[world]
[17:19:21] [Server thread/INFO] [minecraft/LivingEntity]: Named entity SmallSlime['Natalia'/1012, l='ServerLevel[world]', x=-410.21, y=18.50, z=878.79, tamed=true, owner='0eff77b4-8a38-45fc-a540-35467bd2049f'] died: Natalia drowned
[17:19:35] [Server thread/INFO] [Bo's Player Companions/]: Spawn 076a81b0-07d2-430b-a042-84afb45177ba BlockPos{x=-411, y=19, z=880} ServerPlayer['Wally720'/354, l='ServerLevel[world]', x=-411.49, y=20.00, z=878.86] ServerLevel[world]

Is the issue happening in combination with other mods? (If yes, please provide a full list)
Magma server
MC 1.18.2
Player Companion V1.9.0

Additional context

#Player Companion's (General configuration)
[General]
#Respawn companion on death.
respawnOnDeath = false
#Respawn delay in seconds (1200 secs = in-game day).
#Range: 1 ~ 8400
respawnDelay = 1200
#Allow's damage to an owned companion by the owner or their owned companions.
friendlyFire = false

Thanks a lot for the detailed report, this should be fixed with version 6.0.0.

Please keep in mind as soon you set the option respawnOnDeath = false, the player companion could no longer respawned after death, because all relevant information are removed.