Just saw this thread and wanted to chime in because I went down this exact rabbit hole last winter shooting a retirement party. The R7 multi-function shoe has 21 tiny digital pins at the front. Older flash feet can easily bridge those contacts, causing communication errors or even minor short circuits. That is likely why your Godox is dropping connection. If you want absolute reliability for that reunion without messing with adapters, you might want to consider going native with the Canon Speedlite EL-5. It is designed specifically for the new multi-function shoe and talks to the camera digitally. A few things you need to be careful about with this setup:

• It uses the Canon LP-EL Lithium-ion Battery instead of AAs, which gives you insane recycle times (around 1.2 seconds at full power) but means you have to buy spares.
• Compatibility is limited. It only works on newer Canon bodies with the multi-function shoe, so it wont work on older DSLR backups.
• The locking mechanism is a dust- and water-resistant lever that seals tightly, but you have to make sure the shoe cover on your R7 is clean before mounting it. It is right at the top of your $300 budget if you find a sale, but avoiding the headache of missed family moments is totally worth it.

I went through this too. I suggest the Godox V860III-C TTL Flash for Canon. Just be careful to:

• slide it fully forward in the shoe
• lock it down tight

bump