Firefox gives "301 Moved permanently" error on Http Request - json

Question

I am currently developping an Angular 4 chat application, which make severals HTTP request.
On Google Chrome or Opera browser, all requests work fine but when I test my app on Firefox, one of them doesn't pass. I have already cleared my cache many times but the problem persists.
this.chatWebService.getLatestConversations(params).subscribe(
(response: CustomHttpResponse<ConversationModel[]>) => {
this.chatSharedService.setDiscussionList(response.data);
},
(errorResponse: HttpErrorResponse) => {
console.log(errorResponse)
});
And the request:
public getLatestConversations(p: { filter: string, search: string, page_index: number, page_count: number }): Observable<{}> {
const url = `${this.messagesUrl}?filter=${p.filter}&search=${p.search}&page_index=${p.page_index}&page_count=${p.page_count}`;
return this.http.get(url, { params: this.createHttpParams(p) });
}
private createHttpParams(params: {}): HttpParams {
const searchParams = new HttpParams();
const keys = Object.keys(params);
keys.forEach(key => searchParams.append(key, String(params[key])));
return searchParams;
}
On Firefox, this code gives me this error:
SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of
the JSON data
Here is a sample of the returned JSON data:
{
"data": [
{
"type": "user",
"id": 76,
"name": "User 1",
"slug": "razx6k5nuser",
"muted": false,
"messages": [
{
"content": "Hi there",
"media": false,
"sent": 1516372902,
"read": true,
"sender": {
"id": 76,
"slug": "razx6k5nuser",
"lastname": "User lastname",
"firstname": "User first name",
"phoneNumber": ""
}
}
]
},
{
"type": "user",
"id": 71,
"name": "User 2",
"slug": "volc6p1suser",
"muted": false,
"messages": [
{
"content": "new message",
"media": false,
"sent": 1516358686,
"read": false,
"sender": {
"id": 77,
"slug": "razv6i2auser",
"lastname": "User lastname",
"firstname": "User first name",
"phoneNumber": ""
}
}
]
}
],
"meta": {
"page": "1",
"total": 18,
"totalNotRead": 1,
"totalMuted": 0
}
}
According to some errors I found on Google, it seems be solved by adding some headers for each request, so I have already added some headers on each of request with the interceptor, like this:
const request = req.clone({
setHeaders: {
'Content-Type': 'application/json',
'Accept': 'application/json'
}
});
But it still doesn't work. Can someone help me? Thank you in advance.