KSP 1.11.x has a bug, that causes disconecting strut connectors and fuel lines connected during EVA construction mode after reloading save file. This is due to a wrong paring of MissionID and CraftID of the connector's target (the second end).
This mod work around that bug by changing MissionID of whole strut connector so both ends of strut connector has the same MissionID and KSP can connect it after loading a vessel.
Thanks to @dpirch for finding easy fix by changing of MissionID,
Mod does two things:
It fixes connector's MissionID instatnly when they are connected during EVA Construction mod
After loading a save file and creating FlightGlobals (usually this is done when you start fly some vessel), it parse all "unloaded vessels" (=not actual flying vessel or nearby one) and tries to pair targets of strut connectors with a correspondig part. This can be done only when the target part's CraftId is unique for that vessel. For example when you will have two identical vessels docked together, all CraftIDs will be duplicated so correction cannot be done.
Spacedock: https://spacedock.info/mod/2714/Bugfix for disconecting struct and fuel lines
Download from Github https://github.com/xmnovotny/KSP-CModuleLinkedMeshFix/releases/download/1.0/CModuleLinkedMeshFix-1.0.zip
License: GPL 3.0
Installation: Extract the archive so that CModuleLinkedMeshFix directory should end up directly under GameData.
Usage: No interaction is required.