If you trigger the shield from the Tightly Wound Coil and use the Shielded Heart relic, the Shielded Heart will provide no additional shield. Subsequent uses of Shielded Heart also provide no visible shielding.
brazen sequoia
If you trigger the shield from the Tightly Wound Coil and use the Shielded Heart relic, the Shielded Heart will provide no additional shield. Subsequent uses of Shielded Heart also provide no visible shielding.
remote zinc
slate cypress
This happened to me as well; running Tightly Wound Coil, Energy Diverter, and Shielded Heart.
left marten
can confirm, also the interaction works if you use the relic first and then shoot, but not viceversa