Have similar issue while connect 1-wire sensors to pins 4 (power) and 5 (data) for low energy sensor.
Looks like at least pin 5 used internally (as LED ?) by MySensors and broke 1-wire i/o.
After moving 1-wire "data" pin to "A1" and hardwire "power" pin to "VCC" I have no issues with DS18B20. But about 3.5uA per sensor more in sleep (11-12uA instead of 4.7).
BTW: still have issue with node registration and/or other connection issues - after approx. 2 days node whan't to send data to gateway... Will debug later.
PS: MySensors v2.0 from Arduino Lib manager, Arduino Pro Mini 3.3V@8MHz@4.1VLiPo