I hope I am doing this right and in the correct place here - I am new to this forum.

I upgraded to zotero 5.0.34 today after experiencing the below problems but unfortunately they weren't solved.
The error ID is as in the topic title: 1548212267

When trying to migrate a large library from a bibtex file generated with endnote I repeatedly got import errors from zotero so I tried to find the source by decreasing the number of entries in the file. That didn't help. Below is the most steps I went through with zotero after restarting it:
- I opened the zotero desktop application.
- by right clicking on it I tried to export a single article with better bibtex (I am only doing this so I have a reliable bibtex source file for later reimporting)
- I received the error message "An error occurred while trying to export the selected file." and an empty file was generated (checked by opening with Notepad)
- by right clicking on the same article I exported it using the bibtex option (without the better)
- file was successfully generated and contained content (checked with Notepad again)
- I imported the same file with better bibtex option
- I received the error message "An error occurred while trying to import the selected file. Please ensure that the file is valid and try again."
- I imported the same file with only the bibtex option (without the better - also excluding notes to be imported)
- I received the same error message "An error occurred while trying to import the selected file. Please ensure that the file is valid and try again."
- I opened the file with notepad and copied the entry to the clpboard:
@article{classen_2d_2010,
title = {2D electron cyclotron emission imaging at {ASDEX} {Upgrade} (invited)a)},
volume = {81},
issn = {0034-6748, 1089-7623},
url = {http://scitation.aip.org/content/aip/journal/rsi/81/10/10.1063/1.3483214},
doi = {10.1063/1.3483214},
abstract = {The newly installed electron cyclotron emission imagingdiagnostic on ASDEX Upgrade provides measurements of the 2D electron temperature dynamics with high spatial and temporal resolution. An overview of the technical and experimental properties of the system is presented. These properties are illustrated by the measurements of the edge localized mode and the reversed shear Alfvén eigenmode, showing both the advantage of having a two-dimensional (2D) measurement, as well as some of the limitations of electron cyclotron emission measurements. Furthermore, the application of singular value decomposition as a powerful tool for analyzing and filtering 2D data is presented.},
number = {10},
urldate = {2016-02-05},
journal = {Review of Scientific Instruments},
author = {Classen, I. G. J. and Boom, J. E. and Suttrop, W. and Schmid, E. and Tobias, B. and Domier, C. W. and Jr, N. C. Luhmann and Donné, A. J. H. and Jaspers, R. J. E. and Vries, P. C. de and Park, H. K. and Munsat, T. and García-Muñoz, M. and Schneider, P. A.},
month = oct,
year = {2010},
keywords = {Plasma diagnostics, Backward wave oscillators, Eigenvalues, Image sensors, Edge localized modes},
pages = {10D929},
file = {Classen et al. - 2010 - 2D electron cyclotron emission imaging at ASDEX Up.pdf:C\:\\Users\\Sven Doenges\\Documents\\Uni\\PhD\\Literature\\Zotero\\storage\\ETTEHZPA\\Classen et al. - 2010 - 2D electron cyclotron emission imaging at ASDEX Up.pdf:application/pdf}
}
- I tried to import from clipboard
- I received the same error message without anything being imported "An error occurred while trying to import the selected file. Please ensure that the file is valid and try again."
- I decreased the amount of information in the file to using wordpad (hoping I didn't create any syntax errors):
@article{classen_2d_2010,
title = {2D electron cyclotron emission imaging at {ASDEX} {Upgrade} (invited)a)},
volume = {81},
issn = {0034-6748, 1089-7623},
url = {http://scitation.aip.org/content/aip/journal/rsi/81/10/10.1063/1.3483214},
doi = {10.1063/1.3483214},
abstract = {The newly installed.},
number = {10},
urldate = {2016-02-05},
journal = {Review of Scientific Instruments},
author = {Classen, I. G. J. and Boom, J. E.},
month = oct,
year = {2010},
keywords = {Plasma diagnostics, Backward wave oscillators, Eigenvalues, Image sensors, Edge localized modes},
pages = {10D929}
}
- I imported the file using bibtex option (without the better - just realizing this is irrelevant because what I mean by this is the dropdown menu in the open file dialog that allows me to filter for only *.bib files which are the same between better bibtex and not better)
- I received an the same error "An error occurred while trying to import the selected file. Please ensure that the file is valid and try again."
- I cpied the above shortened article entry to the clipboard
- I imported the clipboard again
- I received the same error again: "An error occurred while trying to import the selected file. Please ensure that the file is valid and try again."

And now I am not sure what else to try to narrow down the problem further.
After generating the error report I also tried to import from file and clipboard another entry that only had title, author and year in it.
Plus, I tried this with multiple other articles in my zotero library without success, so it is not just that one article that is corrupted.

I hope someone can help me with this.