Your layout needs some improvement: please keep in mind that this is a inductive switching regulator, the layout of which must be carefully planned. E.g. route the feedback trace as far away as possible from power inductors and other noisy power traces, and keep it as short and with low-inductance and with low-resistance as possible.
You can take e.g. a look at the layout of the very similar STEVAL-VP319X1B, especially the application note AN5521. There you will also find the layout as GERBER ZIP file, which you are welcome to adopt and adapt whatever you like.
If you don't have a GERBER viewer, you can use the tool GerbView, for example, which is part of the KiCad program package and is also able to open GERBER ZIP files directly.
Good luck!
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/Peter
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