Firefox vs. Chrome: flex box rendered differently, align-items

[HGZdev]

Div (class="Box3") embedded in other div (class="Box2") are rendered differently by Firefox vs. Chrome, when both of them are displayed flex and all of them are wrapped by another div (class="Box1"). They seem to differently interpret "align-items: center" on "Box2".

https://codepen.io/HGZwebdesign/pen/NwYrwP

[philipwalton]

Thanks for reporting. Can you please update this issue to include all the information outlined in the reporting guidelines. If the issue is no longer relevant, please close it.

[HGZdev]

I'm not sure, which information should be included to this issue. Could you give me some hints?
Please, find below a print screen showing differences between Chrome and Firefox.

[garrettw]

Which one is Chrome and which is Firefox?
Also, has this bug been reported to the dev teams of either browser? If so, please link to the bug reports.

[brmscheiner]

Cannot reproduce on my system. Chrome 70.0.3538.77 on the left Firefox 62.0.3 on the right.