I've used Vegas for many years and I've never had this issue before. This is a new / fresh install of a legit purchase (made via Humble Bundle) for Vegas 14 Pro Edit (build 270) 64bit.

System Specs

Operating System
  Platform: Windows 10.0 (64-bit)
  Version: 10.00.16299
Processor
  Class: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
  Identifier: GenuineIntel
  Number of processors: 8
  MMX available: Yes
  SSE available: Yes
  SSE2 available: Yes
  SSE3 available: Yes
  SSSE3 available: Yes
  SSE4.1 available: Yes
  SSE4.2 available: Yes

Display
  Primary: 1920x1080x32

Memory
  Physical memory: 32,724.8 MB
  Paging memory available: 65,493.0 MB

GPU
  Geforce GTX 1080ti

Disk
  OS and Vegas are installed on SSD (Samsung 950 Pro M.2) The original files being added to the project are on physical 7200rpm disk. Vegas is rendering them ON the SSD however.

I have several video clips recorded from Geforce Experience (1080p @ 60fps) threw them in Vegas with some mild edits - pretty much splits only, no effects just a collage of clips put together (all same source). I render the video and the output is seizure inducing with stuttering / shaking in and out! I've tried numerous default render templates (Intel HEVC, MainConcept AVC/AAC, MPEG2), Windows AVI with various encoders / settings. ALL of them have the same issue.

Things I've tried:

Varying default render templates, Disabled GPU rendering, changed constant video bitrate, tried variable bitrates, tried selecting variable but set the min and max to the same, tried rendering at various FPS, enabled/disabled "Allow source to adjust frame rate", disabled resample everywhere (each clip and the project itself), tried playing the rendered output on numerous players (VLC, Windows Media Player, Quicktime) all have the same stutter, uploaded the file to YouTube and the stutter follows.

Here is one of the original unedited clips as you can see it plays smooth as butter

Here is the rendered output including the above clip and a few others (again all same source / resolution / fps) Again the rendered video local plays the same as on YouTube with this stuttering / shaking.

edit:

If I take the files that came from Geforce Experience and run them thru handbrake (re-encoding them) then and only then will they play smooth within Vegas. I posted this issue on the Geforce forums with hopes they can shed some light on the situation.

I threw one of the files into gspot to try and find its codec info this is what it came up with.

https://i.gyazo.com/0294ccdb49e4b9d467b98a4e06e8d37a.png