When printing paper jams after the second page.

Sounds like you need to adjust the paper thickness.
Here is the manual:
https://content.etilize.com/User-Manual/1018267948.pdf

IF THIS PROBLEM IS PERSISTING THEN YOU WILL HAVE TO OPEN THE PRINTER AND LOOK FOR ANY KIND OF PAPER BITS STUCK TO THE CORNERS OF THE PRINTER FROM INSIDE

check between the rollers there will be small bits of paper jammed in that is the reason.

Its is trick..If its more then two pages print, printer grabs second page even first page in duplex unit., here its confusion. Check with simplex single print, see any paper mismatch error? or printer throwing paper in output bin after successful print?. No.. check fuser out sensor or paper out roller.
Print only two pages matter in duplex, check where paper struck? if paper our roller not grabbing paper back properly in time (slipping while grabbing back) gets jam error.
Always ensure that select proper paper size in printer.Other than this it may major issue, need technical knowledge..& possibilities are less to judge the exact problem..
Keep update us to resolve the issue.

First step is to unplug your printer, leave it unplugged for 30 seconds and then plug it back in.

check the wheels that pick it from the tray.
If they feel smooth, try to put some tape on them and rip it back off.
This cleans the wheels. Also try a new pack of paper and check if it\'s set to plain paper and not to heavier or coated paper

Some printers have setting that as the toner cartridge is low will allow you to only print one. Check your toner...

According to the LexMark support page, this is most often related to not getting the print cartridge assembly properly positioned. (Left and right sides not fully in place). Another possible source is paper in the output tray when using the double sided printing feature. (This leads to grabbing an extra sheet when it tries to retrieve the paper to print the second side. Paper stock thickness will change the number of pages printed before this happens.).

I hope this helps.

try a test page..and see if that flows..

How do you put the paper in?It must either be the paper or the paper feed system.