Hey there!

The Xperia 1 IV has a huge SD card problem. Reads are very slow(around 20MB/s) and writes are completly buggy.

When you start writing large files to the SD card it starts very fast at almost 100MB/s. After 300 to 500MB written the transfer just stops and waits sometimes for up to 10 seconds then starts again.

Currently I'm using a Samsung PRO Plus 512GB (MB-MD512KB) and a SanDisk Extreme 400 GB ( ‎SDSQXA1-400G-GN6MA).

Both cards work fine in my Galaxy S9+, Note 9 and all USB cardreaders I have. Every app has this problem. For filemangers I tried Google Files, Total Commander and Cx File Explorer.

Is there maybe any workaround until Sony releases an update?