With LMD2018, if a TFDMemTable (or other dataset, I presume) is attached to a TLMDDBGrid and a record is inserted or edited, when this record is posted (saved) the dataset moves to the first record. This didn't occurred with LMD2017 or with standard delphi's TDBGrid.
A demo program is attached. Try to insert some records, then move to e.g. the third record, edit it and post, you'll see that with TLMDDBGrid the dataset will move to the first record, while with TDBGrid it will stay on the just edited record. (you can select which grid to use with a radiobutton on the top of the form).