H264 is systems intensive.
It should not be used as a proxy; kind of defeats the purpose.
Mpeg-2 works a treat for proxy editing. There are others.

From the Properties/General

Plug-In
Name: qt7plug.dll
Folder: C:\Program Files\Sony\Vegas Pro 13.0\FileIO Plug-Ins\qt7plug
Format: QuickTime 7
Version: Version 13.0 (Build 428)
Company: Sony Creative Software Inc.

So, yes, it looks like it is using quicktime.

On another edit platform I used for a long time I remember when they went from their own quicktime implementation to using quicktime itself and the use of quicktime as the decoder improved things quite a bit though, at time, it was still quirky.

"H264 is system intensive"

I find that the Resolve created H264 files play back very nicely - picture quality is good and Vegas plays it back in realtime no problem. I've got a pretty robust system and I am talking about a single H264 clip. Once I get more than 10 in the system things crap out.

Unfortunately my source of files must be from Resolve and they have very limited output options. The only compressed files I can get out of Resolve that Vegas will read are Quicktime MPEG4 and H264. The MPEG4 doesn't look very good and Vegas has great difficulty playing them back in real time. If there is motion in the frame Vegas bogs down and can't play it a 23.976 fps. Something is messed up.

I have found that Vegas handles ProRes files really really well and the Properties/General tab reveals:

Plug-In
Name: qt7plug.dll
Folder: C:\Program Files\Sony\Vegas Pro 13.0\FileIO Plug-Ins\qt7plug
Format: QuickTime 7
Version: Version 13.0 (Build 428)
Company: Sony Creative Software Inc.

So it doesn't appear, to me anyway, that it is the Quicktime plugin that is the issue here.

At the moment the only files I can use out of Resolve for proxies in Vegas are uncompressed. This is nasty when, as the case on this particular job, the original files are ProRes - the proxies are 4x the size of the originals. I'd use the originals but they need a LUT applied to them before use.

Resolve export MXF - MXF OP1 and they even have Sony formats but Vegas has troubles with them - hard crash troubles or simply can't read them.

It's a dog's breakfast....

Resolve outputs dnxhd, correct?
The latest avid le codec are free to download.
Oh, you need to "Match Media Settings." Search.

BINGO!

I had tried DNxHD but it wouldn't load in Vegas but your comment about downloading the codecs set the lightbulb off. Great to see Vegas using the codecs installed on the system! Resolve doesn't.

Anyway, rendered out my test batch using Quicktime -DNxHD 8 bit codec and it works like a charm in Vegas. Good solid playback and response. I'll do my job now and see how Plural Eyes works inside of Vegas.

Thanks so much for the suggestions!

p.s. I'm not sure what that last bit was about "Match Media Settings search" but all seems good so far.

Search the forum and Knowledgebase for "MATCH MEDIA SETTINGS."
Nothing too cryptic about that, I trust.

That iteration of the concept was much clearer, thanks.

My woes continue. I rendered out all my proxies and tried to build a fresh project with them. Loading a little less than 20 clips at a time I managed to build a project with 95 clips in it. I saved it as my day1 shoot project. Closed and went to re-open. Crashes on reopening a few times. I've managed to get it open but now the timeline with the 94 clips is exhibiting the same problem it did with the 19 H264 clips.

I'm scratching my head trying to figure out how this Vegas beast handles stuff but I'm stumped.

I'll pick it up next week...

I would re-load windows on a new SSD, keeping your original. Also remove all hardware from the system including Motu, GPU, blackmagic. Then systematically reintegrate each device until you can replicate the problem.

I had an old high end creative card that would crash Vegas 12 and 13 when trying to edit content. Once I removed that hardware and switched back to the default sound card, Vegas stopped crashing. Not saying that is what your problem is, but I drop 20 or more .mov files on the vegas timeline from 3 camera shoots all the time, then render them to xdcam. No problems. If you get the same issue with a new install, my guess is there is a problem with the way those files are being encoded. In my experience Blackmagic is more about marketing and hype than the reality of what they provide.

90 something clips is probably at limit. I have seen reports and tested myself with 50 clips of DNxHD/Prores where the limit was hit. Boith about the same limit give or tak a file. Apparently with AVC/H.264 you can get higher.

Quicktime is 32-bit only and Vegas uses a 32-bit surrogate program (FileIOSurrogate) to talk with Quicktime. Vegas keeps all files open at all times. Quicktime and/or the Qt decoders keep memory open while the file is open. A 32-bit process is limited in the amount of memory it can address. 2GB of virtual address space. The process is not "using" all that address space but it does get allocated. Anyway, when I looked at the Prores/DNxHD limits the 2GB address space was being blown by FileIOSurrogate.

What is the audio format of your MOV AVC/H.264 files. If you can get it into PCM then Vegas should bypass Quicktime and you should not have any problems. Vegas will also directly handle an MP4 with AVC video and AAC audio.

As was stated by musicvid, mpeg-2 should be a better proxy. Can you output XDCAM files. Either in MXF or XDCAM EX MP4 files.