I am using XBee PRO 900HP S3B soldered to a custom board, connected via SPI. Each is configured as an end node, sending a 84-byte long broadcast once per second.
When testing with 3 boards, the 3 XBees start off OK until after anywhere between 5 and 30 minutes one of them freezes (MCU keeps working but XBee freezes). This is resolved only by resetting the module (by disconnecting power or bringing PIN 5 to GND). After reset they go on normally, until another module freezes - it can be the same one or a different one.
When there are only two modules they seem to run fine for a long time.
I have tested with about 10 different boards so it's not an issue of 3 specific devices.
FW version is 1074, the board is powered with 3V without a regulator. I am using Point-Multipoint. As I pointed out, XBees are connected via SPI and an interrupt is used to read out the data. Also, I am using a 4th XBee connected to a USB dongle and sending out data to a PC.
1. Could this issue be caused by unstable voltage?
2. Is using P2MP not suitable for several devices sending data one per second? Even without routers?
I could use some pointers on how to debug this issue.