Steps to reproduce the issue

1 : create an article with several links to anchors into the same article (part1 / part 2 / part 3 / part 4)
2 : create some "back to top" links with an anchor at top of the page
3 : enable Joomla SEF

Expected result

click on link part 2 should lead to "part 2" anchor
"back to top" link should go back to the top
then click to "part 3" should go to Part 3 and so on

Actual result

First click on any link works : you go to the expected part of the article
click on "back to top" : works
second click on another link fails : you don't reach the part you click for
url is correctly rewritten as expected : full SEF url with "#anchor-part3" or "#anchor-part4" at the end
but you stay where you are

If SEF is disabled : everything goes well

System information (as much as possible)

Joomla 3.8.2
problem seen with Firefox, Chrome, Safari, Explorer, Opera

Additional comments

Everything was ok with previous Joomla versions 3.4 and maybe 3.5
I did the automatic upgrades in Joomla Backend when available
The website owner called me for a fix when it was upgraded to 3.8.2 but I'm not sure this is due to this version only. It could happen on 3.5 or 3.6 but not seen actually.

Thanks