Error for every other row not updating

I am using a flow to do the following:

Lots of other things not relevant.
Check if a row is present in a table:

if it isn't add a row onto the first table
get that row
add it into a second table
add it into a third table
update this first table saying the other two updates have been done.

Use a switch to do different things depending on the region:
update a row in the first table to say an email has been sent - This stage fails -
get the row which has been updated
Change a cell based on the organisation name
Make an image for emailing
Make an image for a word document
populate a MS Word Template
send an email with the word document attached.

The flow alternatively succeeds (1) and fails (0) at step 1.5.1 every other row in a pattern as follows. 1,1,0,1,0.

The error message indicates that the row which should have been added at step 1.1 has not been added.

When I reran with the final four rows it again errors with 1,0,1,0.

When I rerun just the failed rows it succeeds 1,1

I thought it might be that attempting to complete the switch step (1.5.1) while it had the file locked for the subsequent apply to each so I set concurrency to 1 but got the same results.

do you think it is to do with the way app access Spreadsheets for the apply to each at the same time as the switch?

I wanted to see what the community thought of my two ideas for the next steps?

add wait steps to try and give the app a chance to allow the excel sheet to unlock
add a rerun step at the end to scoop up failed rows and try to pass the failed rows through the switch again at the end of a run.

1. Every other row not updating overview.png