Limitations in your research are constraints, parameters and requirements.
They could arise from setbacks and problems or be a result of the project specifications for your PhD.
You might acknowledge them, regret them or be frustrated by them.
They could have been anticipated, they might have surprised you or they could be a previously unforeseen complication due to the pandemic.
If your research – and consequently your PhD – has been impacted by limitations then you have to address it at some point in your thesis, and probably also in your viva.
But you get to choose the words you use to describe those limitations. Of course, be honest: but also realise that words mean something, and the words you use help to convince a reader, a listener and also oneself.
So: what words do you choose to use to describe the limitations of your PhD research?