My vehicles kept random despawning during server reboot or login/logoff, and even manually changed lifetime to 3888000 in xml of the vehicle.

xml I've changed
/path to !Workshop/@IRP-Land-Rover-Defender-110/xmls/types.xml

My Server: Dayz Exp linux server
My Mods:
@1966_Ford_Mustang
@Admin_Hatchet
@AdminMarker
@Advanced Weapon Scopes
@Airdrop-Upgraded
@Armored Vehicle Pack
@Banking
@BaseBuildingPlus
@BuilderItems
@BulletStacksPlusPlus
@CarCover
@Care Packages
@Care Packages VPP Map Markers
@CarRadio
@CarVanillaPlus
@CF;@Code Lock
@Community-Online-Tools
@[CrSk] BMW 525i E34
@Dabs Framework
@Dayz Navigation
@Ear-Plugs
@FlipTransport
@GM-Mods: Repair Wells
@GoreZ
@Hacking System
@Hummer_H2_v2
@InventoryPlusPlus
@IRP-Land-Rover-Defender-110
@Mass'sManyItemOverhaul
@Mortys Weapons
@MuchStuffPack
@Notes
@RepairMod
@Server_Information_Panel;@SF_Flags
@SpookArmbands
@SQUAD MSF-C
@TF:Battery Meter
@Trader
@Unlimited Stamina
@VanillaPlusPlusMap
@ViewInventoryAnimation
@VPPAdminTools
@VPPNotifications
@ZenCarHorn