authoryear in class definition \citet{Author1} results in Author1 u. a. (German not English)

[Nixonst]

When authoryear bibliography type is selected and one uses \citet{} it results in the German and not the English abbreviation of et al. I have tried simply putting \usepackage[english]{babel} in the preamble but doesn't help. Any advice would be much appreciated

[GR8DAN]

Does the same occur for citep{}? Haven't tested this current template, I use a modified template in Overleaf, where the bibliography code has been changed in preamble.tex and thesis.tex, and the et al. appears correctly when cite style is set to authoryear (\setcitestyle{authoryear}).