Very old Cat5 is dodgy, but 5e is normally fine for short runs.
Good advice to check each segment individually, as I wasn't getting gigabit across the house in both directions, but found it was due to one cable that had been kinked too hard and lost a pair. Ironically was a short bit of still shiny new cable, not the 30m segment of older very much used looking wire which had been bent around lots of corners in my old house. Replacing that 5m section gave me ~970mbs each way.
---druck