First char appears twice when searching in "Save as..." dialog in every application

[donquixote]

Steps to reproduce:
- Open a document or web page in an application with a "Save as..." function. Possible examples I tried are LibreOffice Calc and Brave browser.
- Hit "Save as.."
- In the file list below, navigate to to a directory that is not empty.
- Select one of the files or directories to make sure the list has focus.
- Type some letters, e.g. "test".

Expected behavior:
- Search field appears to filter the list of files and directories.
- Search string is "test".

Actual behavior:
- Search field appears to filter the list of files and directories.
- Search string is "ttest", with the first letter appearing twice.

Note:
This only happens if you follow the instructions above.

Ubuntu 18.04.3 LTS
MATE desktop

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: libreoffice-core 1:6.0.7-0ubuntu0.18.04.10
ProcVersionSignature: Ubuntu 4.15.0-72.81-generic 4.15.18
Uname: Linux 4.15.0-72-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CurrentDesktop: MATE
Date: Mon Dec 16 18:42:16 2019
ExecutablePath: /usr/lib/libreoffice/program/soffice.bin
InstallationDate: Installed on 2019-01-12 (337 days ago)
InstallationMedia: Ubuntu-MATE 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: libreoffice
UpgradeStatus: No upgrade log present (probably fresh install)

[donquixote (lemon-head-bw)]

The info above was collected from the "Save as.." dialog in LibreOffice Calc.
However this appears across applications, so I don't think LibreOffice is responsible.