Update failing consistently

[Malcolm Storey]

FileZilla is consistently failing to update on two different W10 PC's and has been for some weeks (I don't use it very often).

Started update check on 2018-06-20 09:41:40
Own build type: official
Downloading /update.php?platform=x86_64-w64-mingw32&version=3.31.0&osversion=10.0&osarch=64&updated=1&cpuid=sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,aes,pclmulqdq,rdrnd,bmi2,bmi2,adx&initial=0
Resolving address of update.filezilla-project.org
Connecting to 136.243.154.122:443...
Connection established, initializing TLS...
Verifying certificate...
TLS connection established, sending HTTP request
File transfer successful, transferred 20,748 bytes in 1 second
Parsing 20748 bytes of version information.
Found new nightly 2018-06-20
Found new release 3.34.0
Downloading /FileZilla_3.34.0_win64-setup.exe
Resolving address of dl2.cdn.filezilla-project.org
Connecting to 78.46.136.26:443...
Connection established, initializing TLS...
Verifying certificate...
TLS connection established, sending HTTP request
File transfer successful, transferred 7,922,200 bytes in 16 seconds
Local size of 'C:\Users\Malcolm\AppData\Local\Temp\fzupdate_d0c97abf64ea84be.tmp' does not match expected size: 0 != 7922200

There is no file of that name in Temp, although it appears briefly during the download. 8MB in 16 seconds is exactly right for our 4Mbps copper, so something's deleting the file.

[Tim Kosse]

Are you using any virus scanners? Try disabling them for a test.

[Malcolm Storey]

You're right! Many thanks.
In case it helps: I'm using Avast (free version). It was blocked by "Behaviour Shield".
Thanks again.