iOS GCM: CIQ settings (strings) do not accept +, %, < and > characters

iOS Garmin Connect Mobile: app settings (strings) do not accept +, %, < and > characters.

Environment
iOS 10.3.1 (iPhone)
Garmin Connect Mobile: 3.19

Description
Entering certain characters in CIQ app settings (string properties) causes unexpected behaviour. As far as I know, it doesn't matter which app you use, as long as it has a string setting.

The behaviour is slightly different for each of the characters.

"+": The string property is sucessfully saved (based on GCM's response and observed app behaviour), but when you re-enter the settings page, the "+" has been replaced with a space.
e.g. Original string: "1 + 2"
New string: "1 2"

"%": The string property is sucessfully saved (based on GCM's response and observed app behaviour), but when you re-enter the settings page, all settings are displayed with default values, including any other settings that had been previously and independently saved.
e.g. Original string: "10 % 3"
New string: Default Value

"<" and ">": The user is presented with a Connect IQ store webpage which says "Sorry, this page is currently unavailable". Settings are not saved (based on observed app behaviour). When you re-enter the settings page, all settings have their previous values.
e.g. Original string: "5 > 3"

All of these characters work fine in the simulator and Garmin Express.

Recreation procedure
In GCM, select an installed CIQ app that has a string setting. It would helpful if the app has more than one setting, in order to verify the behaviour for "%" where all settings are displayed with defaults after saving and re-entering the settings page.

Enter an example string in that field, and tap "Save". If desired, launch the app and verify the settings were actually saved (or not), as described above. (Settings should be saved for all chars except "<" and ">")

Repeat for each of the examples.

e.g. Training Notes:
https://apps.garmin.com/en-GB/apps/e...9-fe49891d7e76

Any one of the "Line" fields, which are strings, will exhibit the behaviour described above.