Error when migrating InfluxDB 1.x to 2.x: Data export only provides a small amount of data

Hello,
I installed the InfluxDB v1 AddOn and used it to collect data in the standard “autogen” retention for 8 measurements for half a year (year 2024).
Now I want to switch to InfluxDB v2 and have installed this add-on with a different port in parallel:

image

I’ve already searched a lot on the Internet, Influx documentation and relevant forums and tried the following two ways to export my data from InfluxDB v1:

influx_inspect export -database <MyInfluxDB> -retention autogen -out /data/exports/influxdb -lponly -datadir /data/influxb -waldir /data/influxdb/wal

and

influxd backup -portable -database <MyInfluxDB> <path-to-backup>

I “experimented” with the parameters for both variants.
My problem:
In principle it works, but only the last few days (July) are exported. The “influx_inspect export” delivers a readable file. In this I looked at the epoch timestamps and found that only the last few days were being exported.
The file or files are created in about 1-2 seconds with both methods mentioned above and when exported it is only about 40 MB in size.
As I said, the DB actually contains 8 measurements over half a year.
I read that there is a file size limit of 10 MB when importing with “influx write” and that you have to split the export beforehand.

But why isn’t all the data exported when I do this?
I’m grateful for every hint.
What else can I check if necessary?

I would first like to test the migration from v1 to v2 and the connection of Influx v2 to Grafana. Until then, Home Assistant should continue to collect the data in Influx v1. Only when I know it works would I want to completely move to v2.

Thanks for your tips.