Dell Precision 3450 i7-11700 - Memory performance troubles Gear2 and CR:2T never gets to 50GB/s, max is 40GB/s for 3200 dual ch

Hello,

I've got into little bit of troubles with finding right RAM modules for Dell Precision 3450 machine,

All configurations are running in Dual channel mode (therefore this part is fine)
but with two identical sticks (same pair / manufacturer-capacity-model-speed) it's always switches into Gear 2 slow mode (command rate or CR = 1T) while if I mix two sets (right slots in pair, therefore still dual channel mode) - it goes correctly into Gear 1 but switches into CR=2T (so one setting gets into better/faster state, but second gets into slower mode) and the worst part - it switches into DDR4-2933Mhz (despite all 4 modules ranked as 3200 RAM { native JEDEC, no XMP })
All modules are 1Rx8 (with 2GB chips)

The stock ones (Dell has supplied machine with) are showing worst performance in benchmarks.
Tried updating BIOS to latest version (although it lists only security advisory improvements, nothing about HW fixes), mixing ram sticks (swapping sequence), nothing changes (and obviously Dell's BIOS doesn't have any memory configuration settings, nor any jumpers on MB).

Is there a way to have 3200 RAM ( 1 Rank, 8 banks ) in CR=1T and Gear 1 mode (closer to proper 50GB/s speed) ?
So far max I'm getting is 20% below nominally advertised speed (around 40GB/s)

First set is 16GB of SK Hynix HMAA1GU6CJR6N-XN ( two of 8GB - 3200 1Rx8 1.2V )
and purchased separately: 32GB of Transcend JM3200HLE-16G ( two of 16GB - 3200 1Rx8 1.2V )

Thank you.