I am debugging a Python (3.5) program with PyCharm (PyCharm Community Edition 2016.2.2 ; Build #PC-162.1812.1, built on August 16, 2016 ; JRE: 1.8.0_76-releas
For me, the solution was removing manual watches every-time before starting to debug. If there were any existing manual watches in the "variables" window then it would remain stuck in "Collecting data...".