When you rapidly switch between a trident and an item like redstone, it is possible to place the redstone without the connections updating properly.
See the attached video
MC-169990
Rapid swap trident/redstone connection placement issue
Open
2
(Unassigned)
Confirmed
Gameplay
Low
Networking, Player
1.15.2 Pre-release 2, 1.17.1
Retrieved
Confirmed. Note this is a visual only issue that disappears after a relog