Steps to reproduce

sent = bot.sendVideo(chat_id=CHANNEL_ID, video=open(myvideofile.mp4, mode='rb'), timeout=5000)

Expected behaviour

Tell us what should happen

Video should upload with a thumbnail.

Actual behaviour

Tell us what happens instead

Video uploads successfully but instead of thumbnail i will get a black square box. This problem happens when video file size > 10MB.
Videos withe less than 10MB shows the thumbnail correctly without any issue.

Configuration

Operating System:
Windows 10 x64

Version of Python, python-telegram-bot & dependencies:

Python 3.6
PTB 10.1.0 - Latest version