I just got into an interesting mess.
I have 3 Arduino's (Pro Mini's) and 2x Teensy's (3.1's) connected via I2C to a Raspberry Pi Master. The 2x Teensy's I2C data lines are connected via OctoBoards but that doesn't really matter since the OctoBoard maps the I2C Pin's of the Teensy to itself. I have 4k7 pullup resistors for SDA/SLC close to the master (also tried on the end - with no effect).
The Arduino's alone are super solid - no issues other than the occasionally I2C lockup when writing data.
The I2C interface has been running for over 3h with no problems.
Now as soon I add a Teensy to it, the bus locks-up and I need to completely shut down everything. Only thing I got to work was direct connection from RPI -> Teensy and even then there were sporadic detection issues.
I tried the Wire lib as well the IC2_T3 lib with no difference. Also tried with 4 different Teensy's with no difference.
Are the Teensy's not compatible with RPI?