Whenever i place a field radio, even if it hasn’t been used or it has only once, it will only be available for that session. When I come back on the next day, their will be no field radios on my map. This has been happening for the last few months
It was always like that and it will probably stay like this.
Besides, compass can display only 8 POI icons, so if you would have 8 active field radios then you would be unable to see there anything else (safehouses, mission markers, etc.)
This is intended game feature. Else-ways, you could cover the whole map with field radios, making movement impossible.