The locking tab of RJ45 plugs breaks very easily. Replace it by two nylon cable ties (aka zip ties), in minutes.

IMPORTANT NOTES:
– This must be regarded as a temporary “Mac Gyver” solution, for home usage.
– Definitely not for IT staff! (no crimper? asking for one in the budget won’t get you fired!)
– Before the tab breaks, consider protecting the plug.

Full article here:
Repair a Broken Ethernet Plug (Instructables)