Fonts issue with bibtex (DEV)

Bibliography entries randomly don't compile throwing the following error (works fine on current master):

To reproduce, try citing the following entry:

@inproceedings{Chang_Watteyne_Wang_Vilajosana_2016, 
  address={Washington, DC, USA}, 
  title={LLSF: Low Latency Scheduling Function for 6TiSCH Networks}, 
  ISBN={978-1-5090-1460-6}, 
  DOI={10.1109/DCOSS.2016.10}, 
  url={http://ieeexplore.ieee.org/document/7536317/}, 
  booktitle={2016 International Conference on Distributed Computing in Sensor Systems (DCOSS)}, 
  publisher={IEEE}, 
  author={Chang, Tengfei and Watteyne, Thomas and Wang, Qin and Vilajosana, Xavier}, 
  year={2016}, month={May}, pages={93–95} 
}