Fatal error:
File appending requested, but 2 of the 5 output files are not present or are
named differently. For safety reasons, GROMACS-2016 and later only allows file
appending to be used when all files have the same names as they had in the
original run. Checkpointing is merely intended for plain continuation of runs.
For safety reasons you must specify all file names (e.g. with -deffnm), and
all these files must match the names used in the run prior to checkpointing
since we will append to them by default. If you used -deffnm and the files
listed above as not present are in fact present, try explicitly specifying
them in respective mdrun options. If the files are not available, you can add
the -noappend flag to mdrun and write separate new parts. For mere
concatenation of files, you should use the gmx trjcat tool instead.