We have changed the diff algorithm we use in pull requests to improve performance on complex diffs, you can check for more details here:
The new algorithm we use does not reflect changes made to the destination branch since the source branch was created from the destination branch, it will show only the changes introduced in the source branch. This is the reason why conflicts cannot be displayed on our website anymore.
We have a request to provide the previous preview-merge diff type on demand that you can vote for if you'd be interested in that (this diff would show conflicts as well):
Beginning on April 4th, we will be implementing push limits. This means that your push cannot be completed if it is over 3.5 GB. If you do attempt to complete a push that is over 3.5 GB, it will fail...