I ran into the issue a few more times but found some kind of fix for it: Just restarting LrTimelapse and opening the containing folder without deleting any edits or re-doing the sequence helped in almost every case.

Apart from the legit error when transitions really cannot be calculated du to too close keyframes (as I explained above), I found a scenario, where this error could pop up unfoundedly in special white balance constellations. This will be fixed in 6.0.4.

LRTimelapse 6.0.4 is now available for download and should fix this issue: https://lrtimelapse.com/download/
I'm looking forward to hear your feedback.

Hi Gunther,

I continue to experience this issue - but this time, I am able to give a bit more context when this issue occurs. I investigated a bit more and found the following:

Sometimes, LrTimelapse does not read the WB settings from the keyframes correctly. Although a custom white balance has been set, the files in LrTimelapse continue to have "Auto". But not all of them. And this is exactly, what causes the failure of transition calculation: Having Auto and Custom White Balance mixed.

For some reason, LrTimelapse does not properly read the saved whitebalance in the XMP files under some circumstances.

Changing the White Balance manually in LrTimelapse for the keyframes resolves the issue. But saving the metadata in Lightroom and reading in LrTimelapse sometimes causes the wrong white balance information in LrTimelapse.

I am using the latest Lightroom and LrTimelapse version. I am currently traveling and have a very slow internet connection. Otherwise I would provide you a screen vide. Let me know if there is anything I could provide to help to resolve this issue.

Do you by chance have "Automatically Save XMP Metadata" activated in the Lightroom settings? Please double check, that must be off.

If not:

Is it just random images where the WB ist not being read correctly or is there a pattern? Could you please explain the scenario a bit more in detail so that I could try to reproduce?

Start with the WB mode that the files have after loading them. Let me know which file type you are using and how you proceed through the workflow. An info might help.