Impress very slow

I use LibreOffice some, not a lot. I run on fully patched Ubuntu 20.04. I have a 8 core 16 thread AMD Ryzen 2700x with 32 GB RAM and a solid state ATA attached 1 TB disk. Almost always everything runs really quick including LibreOffice Writer when I use it. But using Impress to make slides is always very slow. Opening a .ppt file created by Impress which has maybe 5 simple slides with nothing but text, maybe 2 font sizes, one color, no images, no video, takes perhaps 4 seconds. It actually initially opens very quickly but to “show” the 5 slides in the left side overview window takes the 4 seconds. If I make a simple change, maybe add one letter to one slide then when I save as .ppt (or any other slide format, I tried several) it will take perhaps 7 seconds. Then if I close Impress (not making other changes to need saving) it will take perhaps another 4 seconds. And its always this slow on various Impress created files from 2 to 20 slides each. But again Writer is always nice and quick. I checked the memory usage and there is tons of memory available from the 32 GB I have. The CPU usage graph shows lots of CPU usage on one core along with multiple cores showing some usage when Impress is doing its slow thing. Otherwise there is almost not CPU usage.I noticed the OpenOffice process soffice.bin seems to be using the my Nvidia GeForce GTX 1050 Ti graphics card directly by way of OpenCL. Any idea on why Impress is so slow while everything else including Writer is fast?

Additional information. I have some old .ppt files I created in 2008 with an older version of LibreOffice (could have been OpenOffice back then). If I open them in this newer Impress its very fast, like it should be. Still just simple slides, nothing fancy. All text, no pictures, no video. So why is a .ppt file created in 2008 fast while one created in 2021 slow?

Another update. Apparently the slowness is related to the template. I used Blue Curve and I can get that template to be slow, its repeatable. If I use other templates, its fast. I don’t know what the problem is with Blue Curve but I tested changing an existing presentation to Alizarin and now its very fast.