It resets to zero

Works fine for me. Some other mod is probably interfering. Please post your list of mods.

is there an easy way to copy them rather than just uploading the json ?

If you're running so many mods that this is an issue, I probably can't help you anyway. If you can narrow down exactly which mod (or mods) make this problem reproducible, I can look into it more.

Do you happen to know of a mod that may interfere? - that'd help me narrow it down

Not specifically but any mods that affect the rocket silo are good places to start.

the issue seems to have resolved itself, presumably due to some of several mods being updated recently.

For reference though:
If i hover over the rocket silo, the following are listed;
PlanetsLib
Orbital Cannon
Krastorio 2 Spaced Out
Surface Restrictions? Never heard of
Combat Mechanics Overhauled
Maraxis
Muluna

Additionally i have these:
Rocket Cargo Insertion
Igrys

But since it doesn't seem to happen anymore, I got no more info on the temporary issue.