[Bug]: Severe page-navigation lag when opening the same PDF in two tabs Firefox/pdf.js tabs

[Andhu7]

I’m observing significant rendering delays when navigating pages in a PDF document when multiple instances of the same PDF are opened simultaneously in Firefox or in the official pdf.js viewer.
When opening only one instance of the PDF, page navigation is reasonably fast (about ~1 second delay between pages, which is acceptable).
However, when I open two or more tabs showing the same PDF (or the official pdf.js viewer), the page navigation slows down dramatically to 6–8 seconds per page.
This issue seems to scale with the number of simultaneous viewer instances, which suggests some resource contention or shared worker limitation.

Web browser and its version

Mozilla firefox 145.0

Operating system and its version

Windows 11

PDF.js version

https://mozilla.github.io/pdf.js/web/viewer.html

Is the bug present in the latest PDF.js version?

Yes

Is a browser extension

No

Steps to reproduce the problem

Open Firefox.
Open the PDF in a tab (either directly in Firefox’s built-in PDF viewer or via https://mozilla.github.io/pdf.js/web/viewer.html).
Navigate between pages — notice rendering time is ~1 second.
Now open another tab with the same PDF (or another copy of the same viewer).
Navigate between pages again in any of the tabs.
The rendering delay jumps to 6–8 seconds per page.

What is the expected behavior?

Page rendering time should remain consistent regardless of how many tabs have the PDF open.

What went wrong?

Even with 2 tabs page rendering is causing around 5 6 seconds of delay

Link to a viewer

No response

Additional context

No response