Paying for 100Mb upload, getting 40Mb upload on Xfinity modem in bridge mode

Hello,

I am getting upload speed below contract terms when testing against two different speed testing sites - 40Mb from Ookla, 60Mb from Google.  I am paying for 100Mb.

I have an Xfinity modem currently in bridge mode.

I am testing directly from my router.  

Download speeds are acceptable to contract terms.

Any advice on this?  Are there any settings on the gateway I can manipulate to try to troubleshoot this?  It seems that I have zero ability to modify any controls on the gateway currently.