Using Firefox Nightly.
mozregression says it started happening in this range of the 2020-03-10 nightly build:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=3004bc7597a088e181fbcb9a9044b8d952e9d45f&tochange=5b47cfcab1554c89400b7a6299ff0cabac4bda0c

Steps to reproduce:

1. Open a new tab.
2. Visit google.com
3. Search for something.
4. Close tab.
5. Press Ctrl+Shift+T (on Linux)

Result:
The tab will reopen. The location bar will briefly show the correct URL with the search query, but will then switch back to google.com and show that page.

Expected result:
The tab should reopen on the search query result.

I couldn't manage to reproduce it with a brand new profile, but it happens in several other profiles I use, one of them with no settings changes, created in the past few weeks.

I can reproduce the issue on Nightly76.0a1 windows10 if set "New Tabs" to "Blank Page" in about:preferences#home

Another scenario
"Restore Previous Session" is also affected.

STR:

1. set "New Tabs" to "Blank Page" in about:preferences#home
2. Open NewTab
3. Visit google.com
4. Search for something.
5. Quit Browser
6. Relaunch Browser
7. Perform "Restore Previous Session"

This effectively also undoes the change introduced in 3166149f37f1 (bug 1615302),
and makes it so that instead of ignoring the userTyped values, we clear them
out in the parent when doing a process flip before sending them down to
the new child process.

https://hg.mozilla.org/mozilla-central/rev/cabf2a947f7e

Reproduced the issue using Firefox 76.0a1 (20200403214010) on Windows 10x64 and steps from comment 0 and 1.
The issue is verified fixed using Firefox 78.0 (20200625152958) and Firefox 77.0a1 (20200407093520) from comment 5.