The following json with an integer in Firefox:
{"inventoryIds":15369683015733721}
parses the numeric value as 15369683015733720
This behavior has not been observed in other numeric values (so far).
To replicate: Save the json on disk and load in Firefox. The displayed value then looks like:
inventoryIds: 15369683015733720
Work around has been applied by just parsing the data as a string, which solves the issue, but the root cause would be nice to know.
(Same issue occurs in Chrome, tested on Linux (openSuse Leap, and Ubuntu 18.04LTS))