If I have filenames with a dot in them, saving the projects as projectA_v1.1 I have to manually add the extension; projectA_v1.1.tvpp otherwise the part behind the dot will be ignored (interpreted as an erroneous file extension perhaps?) so it will be saved as projectA_v1.tvpp.
Same when rendering. Sc01_example.0001 will be rendered as Sc01_example.png, Sc02_example.png, Sc03_example.png etc. if .png is not added to the name by you.