Clips rendering at different lengths when all the same

I have a timeline set up with 24 clips at 6 seconds each. They are laid out with markers at 6 second intervals so I make sure they really are 6 seconds lond. They are all the same frame rate, from the same camera and with only light color grading done, some clips have had their speeds changed with the retime controls setting, just percentages, no ramping nothing crazy. When I render they all come out at different lengths. Some are 12 seconds, some 9, some 5, just all over the place. What is this happening. I've tried changing the render speed lower, adding frame handles. What am I doing wrong, why is this happening? Any help would be appreciated.

Render "individual clip", is a frame to frame rendering engine.
Use "single clip" and mark the clip you want to deliver

Render "individual clip", is a frame to frame rendering engine.
Use "single clip" and mark the clip you want to deliver

So your suggesting render as "single clip" and mark my in and out for the "individual clips" I can see how that would make sense. I will give it a try and see what happens. Hopefully this is the solution. Now the question, why is is doing this? Why would using rendering as "individual clips" change the length of the actual clip? What does "frame to frame rendering engine" mean and how does that affect the final render and affect clip length? Sorry for all the questions, I like to know why things do what they do so I can possibly avoid a issue in the future. Thanks for the help.

Render "individual clip", is a frame to frame rendering engine.
Use "single clip" and mark the clip you want to deliver

That seemed to do the trick, thank you very much. I never would have thought of that, I just assumed doing individual clips was the way it was to be done. Although it is more tedious to go through and put in and out then add to render queue for every clip, at least I know it's going to come out right. Thanks again!

Rendering individual clips is for colour grading round trip workflows. The user manual explains everything but most users don't bother reading it! No offence intended, just observing that a high percentage of forum posts can be answered by reading the relevant user manual pages.

Rendering individual clips is for colour grading round trip workflows. The user manual explains everything but most users don't bother reading it! No offence intended, just observing that a high percentage of forum posts can be answered by reading the relevant user manual pages.

I totally agree that having a in depth knowledge of a 160 plus page manual of a very technical editing program does eliminate the need to ask questions, but until one has that ability it’s a good thing we have forums in order to ask questions. Everyone has to start somewhere when they learn, I’m sure you had questions and probably still do. I don’t get why people comment about people asking questions and saying they could have found it in user guide. That’s what the forum is for, to ask questions and get help. Every post has the question listed as the topic, if I don’t want to answer a question I just don’t click the topic. No offense intended.

No offence taken. I understand completely. The user manual PDF is searchable so I get an answer much faster than a user forum. It's not about knowing everything in the manual.