Hi
@NaturallyDriven,
I've just come back from Paris half marathon yesterday. I was pacing my wife for just sub 2 hours. I felt the quad pain creep up at 4 k and I had to bail out at 17 k only to limp my way back to the hotel unable to bend the knee joint. Of course the issue migrated from one leg to the other as usual

It sound exactly as your first experience.
What I've done both times prior to my travels (my first experience was on a travel to Iceland a month ago decribed in a post just above) was a move my trainerroad workouts so that I could fit in even more HIIT sessions just before travelling.
And in both cases I actually had to bail out due to training fatique (I never cut my sessions short!!! These two times are my first).
Last training before yesterday's half marathon was on thursday. However, in Paris I walked 25 k on Friday and 21 k on Saturday so I was not just sitting around doing nothing - no issue there.
I am also wondering if this is a bad strategy. And I do certainly not want to end up with Rhabdo. My urine is NOT red or cola colored which often seems to be the case.
I am wondering if I should actually cut down on the cycling and increase the running instead. Maybe also add some weekly rest days.
For reference I am a 44 year old male. Doing Trainerroad structured workouts (ERG mode) on Monday, Wednesday, Friday, and Saturday (long ride 2 hours). I am running on Tuesday, Thursday and Sunday (long run approx 2 hours).
I am also doing weight lifting on Tuesday, Thursday and Sunday, so I do not believe it is an "untrained/lacking strength" issue.
I have run multiple half marathons before and much faster with the issue never happening before.
It is ONLY after I began cycling intensively, which I picked up due to shin splints from running, that I have experienced it.