Hi,
I have never really had any issues transferring via Wi-Fi with my Fenix5X, however since I purchased a 530 for cycling, my Fenix hangs for ages with the spinning dial and "transferring" showing. Its like this for what seems about 5 minutes and when I go into Garmin Connect it hasn't uploaded the data.
I can however download/transfer via my iPhone.
The 530 downloads via Wi-Fi without issue.
I am wondering if it could be something to do with True up linking the two units and something is stalling?