Why does LCC slow export

At work I have a new 64-core AMD Ryzen Threadripper, Windows 10 64-bit, computer with a RTX 3090 GPU, with 128GB RAM. It is used for focus stacking. So I need to export large numbers of TIFFs as fast as possible.
We have been using Capture One since 2015, starting with version 8.

Usually our subjects are small, pinned insects on an even grey background. Early on we found LCCs very useful for producing a lovely, even background. We even used it successfully to even out room light on a second setup to digitise 30,000 archival documents.

Everything worked well until an update half-way through the year of version 11. I believe something changed in the way LCCs were made and we started getting error messages every time we made one on a neutral background.

We also experienced intermittent slowdowns when exporting TIFF source images. I raised several service tickets over the years but the problem was never properly resolved. On the computer I had before this, an i9 10-core, with two 1080Ti GPUs and 64 GB RAM, the export rate went down from one every second to one every four seconds. Since I was photographing peacock spider abdomens, requiring two stacks of 500 source images each, which were late merged in Photoshop, this slowdown wasted nearly an hour on each major image. As this was a contract job it caused a lot of grief.

As the computer was 3 years old by that stage, we replaced it with the current one. After some difficulties with a Nvidia driver conflict, I have rolled back to the previous version. 

The system exports 50-MP blank test images as 16-bit TIFFs at the rate of one every 0.46 seconds. I took a set of images of a fly and tried adding various adjustments, one at a time. Export speed remained the same until I applied an LCC. The LCC was made using an image of a neutral grey background, taken under the same lighting conditions. The LCC has this warning: "Lens Cast Calibration contains clipped data. Bad color casts may occur."

Is the error in the LCC causing the slowdown in TIFF export or does using an LCC always slow down the export rate? If I remember rightly this slowdown did not occur in older versions of Capture One before version 11.