Hello Yaw,
thanks for your hints.
I haven't found any timeouts or similar warnings in tomcat and apache logs. I also just tried again sending our form with 4 attached photos of about 15MB - it took many seconds to upload, but it worked without problems.
I actually also cannot find those errors 400 in the logs for /odk/formList. I only see them on screenshot of ODK Collect from users.
I find regularly this in catalina.out:
WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
- We use https and any request to http is redirect to https - I tested both URLs in the ODK Collect config and it works for me with both http and https configured.
- I had reports of this error 400 from users in different neworkds - company, home and mobile.
- The only "fix" I got reported so far, was somebody installing the app GeoODK, using the same server config which succeeded - and after that, also ODK Collect started working again. It's quite unbelievable, I know.
- I have reports of the error 400 in ODK Collect v1.21.2, 1.22.2. and 1.22.3.
- Actually, those users having problems are currently using Enketo as a work-around.