react-native fails on bundling - react-native

Question

I hope you can help me with an issue I encountered today and I am totally lost at the moment. I have a react-native project going and yesterday everything was working just fine, but today I was trying to start up the bundler, simulator and so on, but got a strange error instead that leaves me totally in the wild with no real clue where to get into this.
Error message
error: bundling failed: SyntaxError: Unexpected token, expected { (52:36)
at Parser.pp$5.raise (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:4454:13)
at Parser.pp.unexpected (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:1761:8)
at Parser.pp.expect (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:1749:33)
at Parser.pp$1.parseClassBody (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:2436:8)
at Parser.pp$1.parseClass (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:2406:8)
at Parser.pp$1.parseStatement (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:1843:19)
at Parser.pp$1.parseBlockBody (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:2268:21)
at Parser.pp$1.parseTopLevel (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:1778:8)
at Parser.parse (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:1673:17)
at Object.parse (/Users/michel.engelen/...<patchToProject>.../node_modules/babylon/lib/index.js:7305:37) [/Users/michel.engelen/...<patchToProject>.../node_modules/react-native/Libraries/Components/Button.js]
This message pops up in the terminal when entering npm start -- --reset-cache and react-native run-ios afterwards.
Project settings / packages installed
Here are my dependencies inside the package.json:
"dependencies": {
"npm": "6.3.0",
"prop-types": "15.6.2",
"react": "16.3.1",
"react-native": "0.55.4",
"react-native-fontawesome": "5.7.0",
"react-native-remote-svg": "1.2.0",
"react-native-splash-screen": "3.1.1",
"react-navigation": "2.11.2",
"react-redux": "5.0.7",
"redux": "3.7.2",
"redux-thunk": "2.3.0",
"redux-undo": "1.0.0-beta9-9-7"
},
"devDependencies": {
"#babel/core": "7.0.0-beta.56",
"babel-plugin-add-module-exports": "0.2.1",
"babel-preset-es2015": "6.24.1",
"babel-preset-react-native": "4.0.0",
"eslint": "5.3.0",
"eslint-config-google": "0.9.1",
"eslint-plugin-import": "2.13.0",
"eslint-plugin-jsx-a11y": "6.1.1",
"eslint-plugin-react": "7.10.0",
"eslint-plugin-react-native": "3.2.1",
"redux-devtools-extension": "2.13.5"
},
I did not specify ranges on them because that nearly always resulted in strange errors with other bundling issues (not this time though).
efforts to solve this (`til now)
rm -rf node_modules/ package-lock.json
upgrading the packages
removing jest from the dependencies
rm -rf ios/ android/ && react-native eject
reset the branch to a commit in the past that was working for sure
I even used yarn instead of npm during all of these steps to see if it has any impact on the outcome
I even tried to reboot the MacBook, but nothing worked up until now.
I seriously hope that somebody can help me with this, because otherwise I would probably have to redo everything, which would take me a lot of time.