Because if the WDTE bits in CONFIG3 is anything but 0b01 the SEN bit is ignored and the CONFIG block of the code contains _WDT_ON which, according to the .INFO file for the device means
An open-drain or open-collector output pin is driven by a single transistor, which pulls the pin to only one voltage (generally, to ground). When the output device is off, the pin is left floating...
Re: SOLVED - PIC seems to RESET unless I add a PAUSE in Mainloop
I would guess by this bit?
Demon Today, 20:28(p. 163 of datasheet)